Question

Tính nhanh :

                  A=15+22+29+......+127+134=?

Nhớ ghi cách làm cho mình nha ^^

Tìm n:

4ⁿ⁺²  +  4ⁿ⁺³  +  4ⁿ⁺⁴ +  4ⁿ⁺⁵  = 85. (2²⁰¹⁶ : 2²⁰¹² )

Answer 1

\(A=15+22+29+...+127+134\)

\(=\frac{\left(134+15\right)\left[\left(134-15\right):7+1\right]}{2}\)

\(=\frac{149.18}{2}\)

\(=2682:2\)

\(=1341\)

\(b,4^{n+2}+4^{n+3}+4^{n+4}+4^{n+5}=85.\left(2^{2016}:2^{2012}\right)\)

\(\Rightarrow4^n\left(4^2+4^3+4^4+4^5\right)=85.2^4\)

\(\Rightarrow4^n.1360=1360\)

\(\Rightarrow4^n=1=4^0\)

\(\Rightarrow n=0\)

Answer 2

mik ko biết

Answer 3

tinh nhanh:

A=15+22+29+...+127+134

moi so hang cua A hon kem nhau :

22-15=7(don vi)

ta thay day la day so cach deu. vay so so hang cua A la:

               (134-15):7+1=18(so hang)

A bang: (134+15)*18:2=1341