Question

\(\dfrac{x-5}{7}=\dfrac{28}{x-5}\) giúp

Answer 1

\(\Leftrightarrow\left(x-5\right)^2=28.7=196\\ \Leftrightarrow\left(x-5\right)^2=14^2\\ \Leftrightarrow x-5=14\\ \Leftrightarrow x=14+5=19\)

Answer 2

đk x ≠ 5

\(\dfrac{\left(x-5\right)\left(x-5\right)}{7\left(x-5\right)}=\dfrac{28.7}{7.\left(x-5\right)}\\ \left(x-5\right)^2=196\\ \left(x-5\right)^2=14^2\\ x-5=14\\ x=14+5\\ x=19\left(tho\text{a}nm\text{a}n\right)\)

Answer 3

ĐK: \(x\ne5\)

Ta có \(\dfrac{x-5}{7}=\dfrac{28}{x-5}\)

\(\Rightarrow\left(x-5\right)^2=196=14^2\)

TH1: \(x-5=14\Rightarrow x=19\left(TM\right)\)

TH2: \(x-5=-14\Rightarrow x=-9\left(TM\right)\)

Vậy \(x\in\left\{19;-9\right\}\)