Question

tìm x : 

\(\left(\frac{3}{4}\right)^5.x=\left(\frac{3}{4}\right)^7\)

tính nhanh :

5 x 8 + 2 x 5 

5 x 6 + 4 x 5 + 2 x 5

Answer 1

\(\left(\frac{3}{4}\right)^5.x=\left(\frac{3}{4}\right)^7\)

x = \(\left(\frac{3}{4}\right)^7:\left(\frac{3}{4}\right)^5\)

x = \(\frac{1}{16}\)

2)

\(5x8+2x5\)= \(5x\left(8+2\right)=5x10=50\)

\(5x6+4x5+2x5=5x\left(6+4+2\right)\)= \(5x12=60\)

k mik nha mik thề sẽ k lại 

Answer 2

Ta thấy : \(\left(\frac{3}{4}\right)^7=\left(\frac{3}{4}\right)^{5+2}=\left(\frac{3}{4}\right)^5.\left(\frac{3}{4}\right)^2\)

\(\Rightarrow x=\left(\frac{3}{4}\right)^2\)

\(5\times8+2\times5\)

\(\Rightarrow5\times\left(8+2\right)\)

\(\Rightarrow5\times10=50\)