Question

Giải PT:

a) \(\frac{4x}{\sqrt{ }7x-6}\) + \(\frac{4\sqrt{7x-6}}{x}\) = 8

b) \(2x^2+\sqrt{x^2-2x-2}=7x+4x\)

Giúp mình với !!!!!!

Answer 1

a) \(\frac{4x}{\sqrt{7x-6}}+\frac{4\sqrt{7x-6}}{x}=8\) Đặt \(\frac{x}{\sqrt{7x-6}}=t\left(ĐK:t\ge0\right)\Leftrightarrow\frac{1}{t}=\frac{\sqrt{7x-6}}{x}\\ Pt\Leftrightarrow4t+\frac{4}{t}=8\Leftrightarrow4t^2+4-8t=0\Leftrightarrow t=1\left(tm\right)\)

Với 

\(t=1\Leftrightarrow\frac{x}{\sqrt{7x-6}}=1\Leftrightarrow x=\sqrt{7x-6}\Leftrightarrow x^2=7x-6\Leftrightarrow x^2-7x+6=0\Leftrightarrow\left[\begin{array}{nghiempt}x=6\\x=1\end{array}\right.\)

Vậy \(s=\left\{1;6\right\}\)