Question

Bài 1: Tìm x

a) \(\left(x-2\right)^4=256\)

b) \(\frac{x^4}{256}=81\)

c) \(125\left(x+\frac{4}{5}\right)^3=729\)

e) \(7^x+2+7x=50\)

f) \(9.13^{x-1}+\frac{4}{169}.13^{x+1}=2197\)

Answer 1

a) (x-2)\(^4\) = 256

(x-2)\(^4\) = \(4^4\)

x-2=4

x=4+2

x=6

b) \(\dfrac{x^4}{256}=81\)

\(\dfrac{x^4}{4^4}=81\)

\(\dfrac{x}{4}=81\)

x =81.4

x = 324

Answer 2

c) \(125\left(x+\dfrac{4}{5}\right)^3=729\)

\(\left(x+\dfrac{4}{5}\right)^3=729:125=\dfrac{729}{125}\)

\(\left(x+\dfrac{4}{5}\right)^3=\left(\dfrac{9}{5}\right)^3\)

\(x+\dfrac{4}{5}=\dfrac{9}{5}\)

x = \(\dfrac{9}{5}-\dfrac{4}{5}\)

x \(=1\)