Thực hiện phép tính
a) (-3)^2+5.(-2)^3+|-7|-|36|
1 1 1 1
b)——- +——–+———-+…..+———
2 6 12 90
Thực hiện phép tính a) (-3)^2+5.(-2)^3+|-7|-|36| 1 1 1 1 b)——- +——–+———-+…..+———
By Kinsley
`a) (-3)^2+5.(-2)^3+|-7|-|36|`
`=9+5.(-8)+7-36`
`=9-45+7-36`
`=-65`
`b)1/2+1/6+1/12+1/90`
`=90/180+30/180+15/180+2/180`
`=(90+30+15+2)/180`
`=137/180`
a $(-3)^{2}$+5*$(-2)^{3}$+|-7|-|36|
=9+5*(-8)+7-36
=9-40+7-36 = -60
b $\frac{1}{2}$ + $\frac{1}{6}$ + $\frac{1}{12}$+…+$\frac{1}{90}$
= $\frac{1}{1*2}$ + $\frac{1}{2*3}$ + $\frac{1}{3*4}$ +…+ $\frac{1}{9*10}$
= 1- $\frac{1}{2}$ + $\frac{1}{2}$ – $\frac{1}{3}$ + $\frac{1}{3}$ – $\frac{1}{4}$ +…+ $\frac{1}{9}$ – $\frac{1}{10}$
=1- $\frac{1}{10}$= $\frac{9}{10}$