Question

[Bang Bang Vua]

a, (4/5)^2x+7= 625/256

b, 7^x+2 +7^x+1 + 7^x / 57 = 5^2x + 2x+1 + 5^2x+3 / 131

Answer 1

[Nguyễn Lê Phước Thịnh]

a: \(\Leftrightarrow2x+7=-4\)

=>2x=-11

hay x=-11/2

b: \(\Leftrightarrow\dfrac{7^x\cdot49+7^x\cdot7+7^x}{57}=\dfrac{5^{2x}+5^{2x+1}+5^{2x+3}}{131}\)

\(\Leftrightarrow7^x=5^{2x}\)

=>x=0