B=1+3+6+10+15+.........+435
C=1/2+1/6+1/12+1/20+1/30+.........1/870
D=3/4+5/36+7/144+9/400
E=3+4+6+9+13+18+...........+2019
1, Thực hiện phép tính ( tính hợp lý nếu có thể) A, -1/12+4/3 B,(-4/14-3/15)-(1/5-20/35- -1)7 C, 3/5+ -5/20+30/75+ -7/4 D, 5/6. -12/13 + 7/13 E, 2/-9 - 5/-36 - 1/4 F, 2/23 +-5/12+7/18+21/23+ -7/12
c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)
\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)
\(=1-2=-1\)
Giải:
a)-1/12+4/3=-1/12+16/12=15/12=5/4
b)(-4/14-3/15)-(1/5-20/35-(-1)).7
=-17/35-22/35.7
=-17/35-22/5
=-171/35
c)3/5+-5/20+30/75+-7/4
=3/5+-1/4+2/5+-7/4
=(3/5+2/5)+(-1/4+-7/4)
=1+-2
=-1
d)5/6.-12/14+7/13
=-5/7+7/13
=-16/91
e)2/-9-5/-36-1/4
=-1/12-1/4
=-1/3
f)2/23+-5/12+7/18+21/23+-7/12
=(2/23+21/23)+(-5/12+-7/12)+7/18
=1+-1+7/18
=7/18
tính nhanh
1+1+2+2+3+3+4+4+5+5+6+6+7+7+8+9+8+9+10+12+13+14+15+16+17+18+19+20+30+1000000=?
1+1+2+2+3+3+4+4+5+5+6+6+7+7+8+9+8+9+10+12+13+14+15+16+17+18+19+20+30+1000000=10000274
Tính nhanh:
a,1/4+2/5+6/8+9/15+8/1
b,1/2+2/4+3/6+4/8+5/10+6/12+7/14+8/16+9/18+10/20
c,1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/80+81/90
a; \(\dfrac{1}{4}\) + \(\dfrac{2}{5}\) + \(\dfrac{6}{8}\) + \(\dfrac{9}{15}\) + \(\dfrac{8}{1}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{6}{8}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{9}{15}\)) + \(\dfrac{8}{1}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{3}{4}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{3}{5}\)) + 8
= 1 + 1 + 8
= 2 + 8
= 10
b; \(\dfrac{1}{2}\) + \(\dfrac{2}{4}\) + \(\dfrac{3}{6}\) + \(\dfrac{4}{8}\) + \(\dfrac{5}{10}\) + \(\dfrac{6}{12}\) + \(\dfrac{7}{14}\) + \(\dfrac{8}{16}\) + \(\dfrac{10}{20}\)
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x (\(\dfrac{2}{2}\) + \(\dfrac{3}{3}\) + \(\dfrac{4}{4}\) + \(\dfrac{5}{5}\)+ \(\dfrac{6}{6}+\dfrac{7}{7}+\dfrac{8}{8}\) + \(\dfrac{10}{10}\))
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x (1 + 1 +1 + 1+ 1+ 1+ 1 +1)
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x 1 x 8
= \(\dfrac{1}{2}\) + \(\)\(\dfrac{1}{2}\) x 8
= \(\dfrac{1}{2}\) + 4
= \(\dfrac{9}{2}\)
c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
= \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
= \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)
= \(\dfrac{10+10+10+10+5}{10}\)
= \(\dfrac{\left(10+10+10+10\right)+5}{10}\)
= \(\dfrac{10\times4+5}{10}\)
= \(\dfrac{45}{10}\)
= \(\dfrac{9}{2}\)
Tính nhanh:
a,1/4+2/5+6/8+9/15+8/1
b,1/2+2/4+3/6+4/8+5/10+6/12+7/14+8/16+9/18+10/20
c,1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/80+81/90
a; \(\dfrac{1}{4}\) + \(\dfrac{2}{5}\) + \(\dfrac{6}{8}\) + \(\dfrac{9}{15}\) + \(\dfrac{8}{1}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{6}{8}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{9}{15}\)) + 8
= (\(\dfrac{1}{4}\) + \(\dfrac{3}{4}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{3}{5}\)) + 8
= 1 + 1 + 8
= 2 + 8
= 10
b; \(\dfrac{1}{2}\) + \(\dfrac{2}{4}\) + \(\dfrac{3}{6}\) + \(\dfrac{4}{8}\) + \(\dfrac{5}{10}\) + \(\dfrac{6}{12}\) + \(\dfrac{7}{14}\) + \(\dfrac{8}{16}\) + \(\dfrac{9}{18}\) + \(\dfrac{10}{20}\)
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\)
= \(\dfrac{1}{2}\) x 10
= 5
c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
= \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
= \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)
= \(\dfrac{10+10+10+10+5}{10}\)
= \(\dfrac{\left(10+10+10+10\right)+5}{10}\)
= \(\dfrac{10\times4+5}{10}\)
= \(\dfrac{45}{10}\)
= \(\dfrac{9}{2}\)
Bài 2: Viết tiếp 2 số hạng vào dãy số sau:
a) 10, 13, 18, 26, ...
b) 0, 1, 2, 4, 7, 12, ...
c) 0, 1, 4, 9, 18, ...
d) 5, 6, 8, 10, ...
e) 1, 6, 54, 648, ... ...
k) 1, 3, 3, 9, 27,
L) 1, 2, 3, 6, 12, 24....
m) 1, 4, 9, 16, 25, 36,
o) 2, 12, 30, 56, 90,
p) 1, 3, 9, 27, ....
g) 1, 5, 14, 33, 72, h) 2, 20, 56, 110, 182.....
q) 2, 6, 12, 20, 30, ...
t) 6, 24, 60, 120, 210...
a) 10; 13; 18; 26; 36; 52...
c) 0; 1; 4; 9; 16; 25...
m) 1; 4; 9; 16; 25; 36; 49; 64...
p) 1; 3; 9; 27; 81; 243...
ai giúp em câu này đi
a,6/1*3*7+6/3*7*9+6/7*9*13+6/9*13*15+6/13*15*19
b,1/1*3*7+1/3*7*9+1/7*9*13+1/9*13*15+1/13*15*19
c,1/2*4*6+1/4*6*8+1/6*8*10+1/8*10*12*14+...+1/96*98*100
d,5/1*5*8+5/5*8*12+5/8*12*15+...+5/33*36*40
* là dấu nhân / là phần nha
1.3.77−1+3.7.99−3+7.9.1313−7+9.13.1515−9+\frac{19-13}{13.15.19}+13.15.1919−13
=\frac{1}{1.3}-\frac{1}{3.7}+\frac{1}{3.7}-\frac{1}{7.9}+\frac{1}{7.9}-\frac{1}{9.13}+\frac{1}{9.13}-\frac{1}{13.15}+\frac{1}{13.15}-\frac{1}{15.19}=1.31−3.71+3.71−7.91+7.91−9.131+9.131−13.151+13.151−15.191
=\frac{1}{1.3}-\frac{1}{15.19}=\frac{95}{285}-\frac{1}{285}=\frac{94}{285}=1.31−15.191=28595−2851=28594
b,=\frac{1}{6}.\left(\frac{6}{1.3.7}+\frac{6}{3.7.9}+\frac{6}{7.9.13}+\frac{6}{9.13.15}+\frac{6}{13.15.19}\right)b,=61.(1.3.76+3.7.96+7.9.136+9.13.156+13.15.196)
làm giống như trên
c,=\frac{1}{8}.\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{48.49.50}\right)c,=81.(1.2.31+2.3.41+3.4.51+...+48.49.501)
=\frac{1}{16}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+\frac{2}{3.4.5}+...+\frac{2}{48.49.50}\right)=161.(1.2.32+2.3.42+3.4.52+...+48.49.502)
=\frac{1}{16}.\left(\frac{3-1}{1.2.3}+\frac{4-2}{2.3.4}+\frac{5-3}{3.4.5}+...+\frac{50-48}{48.49.50}\right)=161.(1.2.33−1+2.3.44−2+3.4.55−3+...+48.49.5050−48)
=\frac{1}{16}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+\frac{1}{3.4}-\frac{1}{4.5}+...+\frac{1}{48.49}-\frac{1}{49.50}\right)=161.(1.21−2.31+2.31−3.41+3.41−4.51+...+48.491−49.501)
=\frac{1}{16}.\left(\frac{1}{2}-\frac{1}{2450}\right)=\frac{1}{16}.\left(\frac{1225}{2450}-\frac{1}{2450}\right)=\frac{153}{4900}=161.(21−24501)=161.(24501225−24501)=4900153
d,=\frac{5}{7}.\left(\frac{7}{1.5.8}+\frac{7}{5.8.12}+\frac{7}{8.12.15}+...+\frac{7}{33.36.40}\right)d,=75.(1.5.87+5.8.127+8.12.157+...+33.36.407)
=\frac{5}{7}.\left(\frac{8-1}{1.5.8}+\frac{12-5}{5.8.12}+\frac{15-8}{8.12.15}+...+\frac{40-33}{33.36.40}\right)=75.(1.5.88−1+5.8.1212−5+8.12.1515−8+...+33.36.4040−33)
=\frac{5}{7}.\left(\frac{1}{1.5}-\frac{1}{5.8}+\frac{1}{5.8}-\frac{1}{8.12}+\frac{1}{8.12}-\frac{1}{12.15}+...+\frac{1}{33.36}-\frac{1}{36.40}\right)=75.(1.51−5.81+5.81−8.121+8.121−12.151+...+33.361−36.401)
=\frac{5}{7}.\left(\frac{1}{5}-\frac{1}{1440}\right)=\frac{5}{7}.\left(\frac{288}{1440}-\frac{1}{1440}\right)=\frac{41}{288}=75.(51−14401)=75.(1440288−14401)=28841
P/S: . là nhân nha
a) 3/13 + 7/12 - 10/13 + 5/12 | d) -5/10 + 12/28 - 3/27 - 7/18 + 20/35 |
b) 15/24 - 6/26 + 28/48 - 30/39 + 10/24 | e) 1/56 + 1/72 + 1/90 + 1/110 + 1/132+ 1/156 = |
c) -1/2 + 3/7 - 1/9 - 7/18 + 4/7 = |
Bài 1 Tính nhanh
a) -3/7 + 5/13 + 3/7
b) -5/21+-2/21+8/24
c) -5/11+(-6/11+2)
d) (-1/32+1/2)+15/32
e)5/17+ -6/13 + 3/4 + 7/-13+12/17
f) 7/23+-18/18+-4/9+16/23+-5/8
g)1/3+-3/4+3/5+-1/36+1/15+-2/9
h)-1/2+1/3+-1/4+-2/8+4/18+4/9
a)\(-\dfrac{3}{7}+\dfrac{5}{13}+\dfrac{3}{7}\)
=\(\left(-\dfrac{3}{7}+\dfrac{3}{7}\right)+\dfrac{5}{13}\)
=\(0+\dfrac{5}{13}\)
=\(\dfrac{5}{13}\)
Bài 1: Tính hợp lí
1/ (-37) + 14 + 26 + 37
2/ (-24) + 6 + 10 + 24
3/ 15 + 23 + (-25) + (-23)
4/ 60 + 33 + (-50) + (-33)
5/ (-16) + (-209) + (-14) + 209
6/ (-12) + (-13) + 36 + (-11)
7/ -16 + 24 + 16 – 34
8/ 25 + 37 – 48 – 25 – 37
9/ 2575 + 37 – 2576 – 29
10/ 34 + 35 + 36 + 37 – 14 – 15 – 16 – 17
Bài 2: Bỏ ngoặc rồi tính
1/ -7264 + (1543 + 7264)
2/ (144 – 97) – 144
3/ (-145) – (18 – 145)
4/ 111 + (-11 + 27)
5/ (27 + 514) – (486 – 73)
6/ (36 + 79) + (145 – 79 – 36)
7/ 10 – [12 – (- 9 - 1)]
8/ (38 – 29 + 43) – (43 + 38)
9/ 271 – [(-43) + 271 – (-17)]
10/ -144 – [29 – (+144) – (+144)]
Bài 3: Tính tổng các số nguyên x biết:
1/ -20 < x < 21
2/ -18 ≤ x ≤ 17
3/ -27 < x ≤ 27
4/ │x│≤ 3
5/ │-x│< 5
Bài 4: Tính tổng
1/ 1 + (-2) + 3 + (-4) + . . . + 19 + (-20)
2/ 1 – 2 + 3 – 4 + . . . + 99 – 100
3/ 2 – 4 + 6 – 8 + . . . + 48 – 50
4/ – 1 + 3 – 5 + 7 - . . . . + 97 – 99
5/ 1 + 2 – 3 – 4 + . . . . + 97 + 98 – 99 - 100
Bài 5: Tính giá trị của biểu thức
1/ x + 8 – x – 22 với x = 2010
2/ - x – a + 12 + a với x = - 98 ; a = 99
3/ a – m + 7 – 8 + m với a = 1 ; m = - 123
4/ m – 24 – x + 24 + x với x = 37 ; m = 72
5/ (-90) – (y + 10) + 100 với p = -24
Bài 6: Tìm x
1/ -16 + 23 + x = - 16
2/ 2x – 35 = 15
3/ 3x + 17 = 12
4/ │x - 1│= 0
5/ -13 .│x│ = -26
Bài 7: Tính hợp lí
1/ 35. 18 – 5. 7. 28
2/ 45 – 5. (12 + 9)
3/ 24. (16 – 5) – 16. (24 - 5)
4/ 29. (19 – 13) – 19. (29 – 13)
5/ 31. (-18) + 31. ( - 81) – 31
6/ (-12).47 + (-12). 52 + (-12)
7/ 13.(23 + 22) – 3.(17 + 28)
8/ -48 + 48. (-78) + 48.(-21)
Bài 8: Tính
1/ (-6 – 2). (-6 + 2)
2/ (7. 3 – 3) : (-6)
3/ (-5 + 9) . (-4)
4/ 72 : (-6. 2 + 4)
5/ -3. 7 – 4. (-5) + 1
6/ 18 – 10 : (+2) – 7
7/ 15 : (-5).(-3) – 8
8/ (6. 8 – 10 : 5) + 3. (-7)
Bài 9: So sánh
1/ (-99). 98 . (-97) với 0
2/ (-5)(-4)(-3)(-2)(-1) với 0
3/ (-245)(-47)(-199) với
123.(+315)
4/ 2987. (-1974). (+243). 0 với 0
5/ (-12).(-45) : (-27) với │-1│
Bài 13: Tìm x:
1/ (2x – 5) + 17 = 6
Bài 14: Tìm x
1/ x.(x + 7) = 0
2/ 10 – 2(4 – 3x) = -4
3/ - 12 + 3(-x + 7) = -18
4/ 24 : (3x – 2) = -3
5/ -45 : 5.(-3 – 2x) = 3
2/ (x + 12).(x-3) = 0
3/ (-x + 5).(3 – x ) = 0
4/ x.(2 + x).( 7 – x) = 0
5/ (x - 1).(x +2).(-x -3) = 0
Bài 15: Tìm
1/ Ư(10) và B(10)
2/ Ư(+15) và B(+15)
3/ Ư(-24) và B(-24)
4/ ƯC(12; 18)
5/ ƯC(-15; +20)
Bài 16: Tìm x biết
1/ 8 x và x > 0
2/ 12 x và x < 0
3/ -8 x và 12 x
4/ x 4 ; x (-6) và -20 < x < -10
5/ x (-9) ; x (+12) và 20 < x < 50
Bài 17: Viết dười dạng tích các tổng sau:
1/ ab + ac
2/ ab – ac + ad
3/ ax – bx – cx + dx
4/ a(b + c) – d(b + c)
5/ ac – ad + bc – bd
6/ ax + by + bx + ay
Bài 18: Chứng tỏ
1/ (a – b + c) – (a + c) = -b
2/ (a + b) – (b – a) + c = 2a + c
3/ - (a + b – c) + (a – b – c) = -2b
4/ a(b + c) – a(b + d) = a(c – d)
5/ a(b – c) + a(d + c) = a(b + d)
Bài 19: Tìm a biết
1/ a + b – c = 18 với b = 10 ; c = -9
2/ 2a – 3b + c = 0 với b = -2 ; c = 4
3/ 3a – b – 2c = 2 với b = 6 ; c = -1
4/ 12 – a + b + 5c = -1 với b = -7 ; c = 5
5/ 1 – 2b + c – 3a = -9 với b = -3 ; c = -7
Bài 20: Sắp xếp theo thứ tự
* tăng dần
1/ 7; -12 ; +4 ; 0 ; │-8│; -10; -1
2/ -12; │+4│; -5 ; -3 ; +3 ; 0 ; │-5│
* giảm dần
3/ +9 ; -4 ; │-6│; 0 ; -│-5│; -(-12)
4/ -(-3) ; -(+2) ; │-1│; 0 ; +(-5) ; 4 ; │+7│; -8
mình giải từng bài nhá
hả đơn giản