Question

Answer 1

ĐKXĐ: \(x\ne\pm1\)

a) \(A=\dfrac{\left(x+1\right)^2-\left(x-1\right)^2}{\left(x-1\right)\left(x+1\right)}.\dfrac{5\left(x-1\right)}{2x}=\dfrac{4x}{\left(x+1\right)}.\dfrac{5}{2x}=\dfrac{10}{x+1}\)

b) Với \(x=3:A=\dfrac{10}{x+1}=\dfrac{10}{3+1}=\dfrac{10}{4}=\dfrac{5}{2}\)

Với \(x=-1\left(ktm\right)\Rightarrow A\in\left\{\varnothing\right\}\)

c) \(A=\dfrac{10}{x+1}=2\Leftrightarrow10=2\left(x+1\right)\Leftrightarrow2x=8\Leftrightarrow x=4\)