Question

Bài 1:a)2^x.4=128                     b)x¹⁵=x

           c)(2x+1)³=125              d)(x-5)⁴=(x-5)⁶

Answer 1

Bài 1:

\(2^x\cdot4=128\)

\(2^x=32\)

\(2^x=2^5\)

\(\Rightarrow x=5\)

b) \(x^{15}=x\)

\(\Rightarrow x\in\left\{0;1;-1\right\}\)

c) \(\left(2x+1\right)^3=125\)

\(\left(2x+1\right)^3=5^3\)

\(\Rightarrow2x+1=5\)

\(2x=5-1=4\)

\(x=\frac{4}{2}=2\)

d) \(\left(x-5\right)^4=\left(x-5\right)^6\)

\(\left(x-5\right)^2=1\)

\(\left(x-5\right)^2=1^2=\left(-1\right)^2\)

\(\Rightarrow\left[\begin{array}{nghiempt}x-5=1\\x-5=-1\end{array}\right.\Rightarrow\left[\begin{array}{nghiempt}x=6\\x=4\end{array}\right.\)