x- ( 2+ 6 +10 + 14 +...+ 198 ) = 17
2*6*10+6*10*14+10*14*18+...+194*198*202/1*3*5+3*5*7+5*7*9+...+97*99*101
rút gọn
ta có
\(\frac{2.6.10+6.10.14+..+194.198.202}{1.3.5+3.5.7+..+97.99.101}=\frac{8.1.3.5+8.3.5.7+..+8.97.99.101}{1.3.5+3.5.7+..+97.99.101}\)
\(=\frac{8.\left(1.3.5+3.5.7+..+97.99.101\right)}{1.3.5+3.5.7+..+97.99.101}=8\)
2-4-6+8+10-12-14+16+...-198+200+202
tich minh cho minh len thu 8 tren bang sep hang cai
=(2-4-6+8)+(10-12-14+16)+...-(194-196-198+200)+(100+202)
=0+0+...-0+302
có 50 con 0
=0.50+302
=0+302
=302
2-4-6+8+10-12-14-16+...+194-196-198+200+202
bằng 0 à ko phải thì thôi
Bài 2: Thực hiện phép tính ( hợp lý nếu có thể)
a) 12 x 18 + 14 x 3 - 255 : 17
b) 68 + 42 x 5 - ( 198 : 11 - 8 )
c) 13 + 21 x 5 - ( 198 : 11 - 8 )
d) 18 - 4 x (27 - 90 + 73)
e) 15 x ( 27 + 18 +6 ) + 15 x (23+12)
f) 417 + 235 + 583 + 765
g) 5 + 8 + 11 + 14 + … + 38 + 41
a) 12 x 18 + 14 x 3 - 255 : 17
= 216 + 42 - 15
= 243
b) 68 + 42 x 5 - (198 : 11 - 8)
= 68 + 210 - (18 - 8)
= 68 + 210 - 10
= 268
c) 13 + 21 x 5 - (198 : 11 - 8)
= 13 + 105 - (18 - 8)
= 13 + 105 - 10
= 108
TÍNH 2-4-6+8+10-12-14+16+...+194-196-198+200+1000
=(2-4-6+8)+(10-12-14+16)+...+(194-196-198+200)+1000 có 25 nhóm = 0 + 0 + .....+ 0 + 1000 có 25 số 0 = 1000
a,-8/3+7/5+-71/15<x<-13/7+19/14+-7/2
b,-19/6+-15/2+11/3<x<-5/4+19/12+-10/3
c,-6/7+3/35<x<-2/5+3/7
d,x=3/4+1/-12
e,x/14=1/7+-3/14
f,11/18+13/6=85/x
g,8/17+5/17<x/17<6/17+9/17
A=2*6*10+6*10*14+10*14*18+...+194*198*202/1*3*5+3*5*7+5*7*9+..+97*99*101
lam cho minh nhanh len nay minh can ai lam nhanh mink tick cho
A=\(\frac{2.6.10+6.10.14+...+194+198+202}{1.3.5+3.5.7+...+97.99.101}\)\(=\frac{2.2.2\left(1.3.5\right)+2.2.2\left(3.5.7\right)+...+2.2.2\left(97.99.101\right)}{1.3.5+3.5.7+...+97.99.101}\)
\(=\frac{2.2.2\left(1.3.5+3.5.7+...+97.99.101\right)}{1.3.5+3.5.7+...+97.99.101}\)\(=\frac{2.2.2}{1}=8\)
tính nhanh
1/2*3 + 1/6*5 + 1/10*7 + 1/14*9+..+ 1/198*101
\(\frac{1}{2.3}+\frac{1}{6.5}+\frac{1}{10.7}+\frac{1}{14.9}+...+\frac{1}{198.101}\)
= \(2.\left(\frac{1}{2.6}+\frac{1}{6.10}+\frac{1}{10.14}+\frac{1}{14.18}+...+\frac{1}{198.202}\right)\)
= \(2.\frac{1}{4}.\left(\frac{1}{2}-\frac{1}{6}+\frac{1}{6}-\frac{1}{10}+\frac{1}{10}-\frac{1}{14}+\frac{1}{14}-\frac{1}{18}+...+\frac{1}{198}-\frac{1}{202}\right)\)
= \(\frac{1}{2}.\left(\frac{1}{2}-\frac{1}{202}\right)\)
= \(\frac{1}{2}.\frac{50}{101}\)
= \(\frac{25}{101}\)
tính giá trị biểu thức
B = 0 – 2 + 4 – 6 + 2020 – 2022
C = 1 – 2 – 3 – 4 + 5 – 6 –7 – 8 + 9 –10 –11 – 12 +…+ 197 – 198 –199 – 200
D =( – 11 – 13 – 15 – …– 99) + (10 + 12 + 14 +…+ 98)
\(C=\left(1-2-3-4\right)+...+\left(197-198-199-200\right)\)
=-8x25=-200
\(D=-\left(11+13+...+99\right)+\left(10+12+...+98\right)\)
=(-1)+(-1)+...+(-1)
=-1x45=-45