Tính:
1+12+13+14+.........+125
12) 17 – 11 – 14 – (-39)
13) −127 - 18.( 5 - 6)
14) 100 + (+430) + 2145 + (-530)
15) (+12).13 + 13.(-22)
16) {[14 : (-2)] + 7} : 2012
17) 13 – 18 – (- 42) - 15
18) 369 – 4[(-5) + 4.(-8)]
19) (-12).(-13) +13.(-29)
20) 125 – 4[ 3 – 7.(-2) ]
21) (-14).9 – 13.(-9) chỉ em với
12) 17 – 11 – 14 – (-39)
=17-11-14+39
=6-14+39
=-8+39
=31
13) −127 - 18.( 5 - 6)
=-127-18.1
=-145
14) 100 + (+430) + 2145 + (-530)
=530+2145-530
=(530-530)+2145
=0+2145
=2145
15) (+12).13 + 13.(-22)
=13.[12+(-22)]
=13.(-10)
=-130
16) {[14 : (-2)] + 7} : 2012
={-7+7}:2012
=0:2012
=0
17) 13 – 18 – (- 42) - 15
=13-18+42-15
=-5+42-15
=37-15
=22
18) 369 – 4[(-5) + 4.(-8)]
=369-4[-5+(-32)]
=369-4(-37)
=369+148
=517
19) (-12).(-13) +13.(-29)
=12.13+13.(-29)=13.[12+(-29)]=13.(-17)=-221
20) 125 – 4[ 3 – 7.(-2) ]
=125-4[3+14]
=125-4.17
=125-68
=57
21) (-14).9 – 13.(-9)
=(-14).9+13.9
=9.[-14+13]
=9.(-1)
=-9
âm 9 nha bạn
tím chữ số tận cùng trong các phép tính sau
a/7^2019
b/12^2019
c/11^8+12^8+13^8+14^8+15^8+16^8
d/11^123+13^124+15^125
a, \(7^{2019}=7^3.7^{2016}=343.\left(7^4\right)^{504}=343.\left(...1\right)^{504}=343.\left(...1\right)=\left(....3\right)\)
b, \(12^{2019}=12^3.12^{2016}=\left(...8\right).\left(12^4\right)^{504}=\left(...8\right).\left(...6\right)^{504}=\left(...8\right).\left(...6\right)=\left(...8\right)\)
c, \(11^8+12^8+13^8+14^8+15^8+16^8\)
\(=\left(...1\right)+\left(12^4\right)^2+\left(13^4\right)^2+\left(...5\right)+\left(...6\right)=\left(....1\right)+\left(....6\right)^2+\left(...1\right)^2+\left(...5\right)+\left(...6\right)\)
\(=\left(....1\right)+\left(....6\right)+\left(...1\right)+\left(...5\right)+\left(...6\right)=\left(...9\right)\)
d, \(11^{123}+13^{124}+15^{125}=\left(....1\right)+\left(13^4\right)^{31}+\left(....5\right)=\left(...1\right)+\left(...1\right)+\left(....5\right)=\left(...7\right)\)
\(a,7^{2019}=\left[7^3\right]^{673}=\overline{....}3^{673}=\overline{....3}\)
Vậy chữ số tận cùng của 72019 là 3
\(b,12^{2019}=\left[12^3\right]^{673}=\overline{....8}^{673}=\overline{....8}\)
Vậy chữ số tận cùng của 122019 là 8
Làm nốt
Tính : 1 - 1 2 ; 1 2 - 1 3 ; 1 3 - 1 4 ; 1 4 - 1 5 ; 1 5 - 1 6
bài 13 : tính tổng
a) S1= 1+2+3+...+999
b) S2= 10+12+14+...+2010
c) S3= 21+23+25...+1001
d) S4= 24+25+26+...+125+126
e) S5= 1+4+7+...+79
Tính bằng cách hợp lý:
a) ( − 125 ) . ( − 5 ) .8. ( − 2 )
b) ( − 127 ) . ( 1 − 582 ) − 582.127
c) ( 43 − 13 ) . ( − 3 ) + 27. ( − 14 − 16 )
d) 125. ( − 61 ) . ( − 2 ) 3 . ( − 1 ) 2 n ( n ∈ ℕ * )
a) ( − 125 ) . ( − 5 ) .8. ( − 2 ) = ( − 125 ) .8. ( − 5 ) . ( − 2 ) = − 1000.10 = − 10000
b) ( − 127 ) . ( 1 − 582 ) − 582.127 = ( − 127 ) . ( − 581 ) − 582.127 = 127.581 − 582.127 = 127 ( 581 − 582 ) = 127. ( − 1 ) = − 127
c) ( 43 − 13 ) . ( − 3 ) + 27. ( − 14 − 16 ) = 30. ( − 3 ) + 27. ( − 30 ) = ( − 30 ) .3 + 27. ( − 30 ) = ( − 30 ) . ( 3 + 27 ) = ( − 30 ) .30 = − 90
d) 125. ( − 61 ) . ( − 2 ) 3 . ( − 1 ) 2 n = 125. ( − 62 ) . ( − 8 ) .1 = 125. ( − 8 ) . ( − 62 ) = − 1000. ( − 62 ) = 62000
Bài 1: Tính nhanh:
a) 2 . 13 . 15 c) 8 . 9 . 125 e) 64 . 125 . 12 g) 4 . 32 . 25 . 125
b) 25 . 17 . 4 d) 7 . 24 . 25 f) 72 . 125 . 3
Bài 2: Tính nhanh :
a) 81. 17 - 2 . 17 + 21 . 17
b) 13 . 24 + 37 . 6 .4 + 12 . 50 . 2
c) 2 . 18 . 14 +3 . 17 . 12 + 4 . 69 . 9
d) 31 . ( 532 + 478 ) + 69 . ( 389 +621 )
e) 3 + 6 +8 +10 +12 + ... +104
Bài 3: Tính tổng ác số hạng của dãy số sau :
A = 1 + 2 + 5 +8 + 11 + ... + 100 + 103
a)2.13.15=(2.15).13
=30.13
=390
không quy đồng tử và mẫu, hãy so sánh các phân số sau.
A)12/13 và 13/14
b)125/251 và 127/153
A) Ta có:
\(\dfrac{12}{13}=\dfrac{13}{13}-\dfrac{1}{13}=1-\dfrac{1}{13}\)
\(\dfrac{13}{14}=\dfrac{14}{14}-\dfrac{1}{14}=1-\dfrac{1}{14}\)
Mà \(1-\dfrac{1}{13}< -\dfrac{1}{14}\)
\(\Rightarrow\dfrac{12}{13}< \dfrac{13}{14}\)
B) Ta có:
\(\dfrac{125}{251}=\dfrac{251}{251}-\dfrac{126}{251}=1-\dfrac{126}{251}\)
\(\dfrac{127}{253}=\dfrac{253}{253}-\dfrac{126}{253}=1-\dfrac{126}{253}\)
Mà: \(1-\dfrac{126}{251}< 1-\dfrac{126}{253}\)
\(\Rightarrow\dfrac{125}{251}< \dfrac{127}{253}\)
Bài 5: Tính hợp lí:
a. (43 − 13) ⋅ (−3) + 27 ⋅ (−14 − 16)
b. (−72) ⋅ (34 − 12) − 34 ⋅ (12 − 72)
c. (−127) ⋅ (1 − 582) − 582.127
d. −225.35 + 225.136 − 225
e. 125. (−7) ⋅ (−2) 3 ⋅ (−1) 2𝑛 (𝑛 ∈ ℕ)
f. 1 − 2 + 3 − 4 + 5 − 6 + ⋯ + 199 − 2
a, (43 - 13).(-3) + 27.(-14 - 16)
= 30.(-3) + 27.(-30)
= - 30.(3 + 27)
= -30.30
= -900
b, (-72).(34 -12) - 34.(12 - 72)
= -72.34 + 72.12 - 34.12 + 34.72
= (-72.34 + 34.72) + 12.(72 - 34)
= 12.38
= 456
c, (-127).(1 - 582) - 582.127
= - 127 + 582.127 - 582.127
= - 127
Tính nhanh:
a) 234-117+(-100)+(-234)
b) -927+1421+930+(-1421)
c)11-12+13-14+15-16+17-18+19-20
d) 101-102-(-103)-104-(-105)-106-(-107)-108-(-109)-110
e) (-125)+100+80+125+20
a) 234 - 117 + (-100) + (-234) = [234 + (-234)] - [117 + (-100)] = 0 + 17 = 17.
b) (-927) + 1421 + 930 + (-1421) = [(-927) + 927)] + (1421 + 930) = 0 + 2351 = 2351.
c) 11 - 12 + 13 - 14 + 15 - 16 + 17 -18 + 19 - 20 = (11 - 20) + (12 - 19) + (13 - 18) + (14 - 17) + (15 - 16)
= (-9) + (-7) + (-5) + (-3) + (-1) = -25.
d) 101 - 102 - (-103) - 104 - (-105) - 106 - (-107) - 108 - (-109) - 110
= (-101) + (-102) + 103 + (-104) + 105 + (-106) + 107 + (-108) + 109 + (-110)
= (-203) + (-205) + (-204) + (-203) + (-110)
= -925.
e) (-125) + 100 + 80 + 125 + 20 = [(-125) + 125] + 100 + (80 + 20) = 0 + 100 + 100 = 200.
Bài 1 : Tính hợp lý (3 tick) :
a) 31 × (-125) + 225 × 31
b) 26 × (-125) – 125 × (-36)
c) 29 × (-13) + 27 × (-29) + (-14) × (-29)
d) 17 × (-37) – 23 × 37 – 46 × (-37)
a ) 31 x ( - 125 ) + 225 x 31
= 31 x [ ( - 125 ) + 225 ]
= 31 x 100
= 3100
b ) 26 x ( - 125 ) - 125 x ( - 36 )
= ( - 26 ) x 125 - 125 x ( - 36 )
= 125 x [ ( - 26 ) - ( - 36 ) ]
= 125 x 10
= 1250
a) 31 × (-125) + 225 × 31
= 31 x ( -125 + 225 )
= 31 x 100
= 3100
b) 26 × (-125) – 125 × (-36)
= -125 ( 26 - 36 )
= 125x 10
= 1250
d) 17 × (-37) – 23 × 37 – 46 × (-37)
= -629 - 851 + 1702
= 1480
a) 31 x (-125) + 225 x 31
= 31 x (-125 + 225)
= 31 x 100
= 3100
b) 26 x (-125) - 125 x (-36)
= 26 x (-125) - (-125) x 36
= (-125) x (26 - 36)
= (-125) x (-10)
= 1250
c) 29 x (-13) + 27 x (-29) + (-14) x (-29)
= (-29) x 13 + 27 x (-29) + (-14) x (-29)
= (-29) x (13 + 27 - 14)
= (-29) x 26
= -754
d) 17 x (-37) - 23 x 37 - 46 x (-37)
= 17 x (-37) - (-23) x (-37) - 46 x (-37)
= (-37) x (17 + 23 - 46)
= (-37) x (-6)
= 222