Question

5x(12x+7)-(3x+1)(20x-5)=-100

Answer 1

Answer 2

\(5x\left(12x+7\right)-\left(3x+1\right)\left(20x-5\right)=-100\\ 60x^2+35x-\left(60x^2-15x+20x-5\right)=-100\\ 60x^2+35x-60x^2+15x-20x+5=-100\\ 30x=-105\\ \Rightarrow x=\frac{-7}{2}\)

Vậy \(x=\frac{-7}{2}\)

Answer 3

\(5x\left(12x+7\right)-\left(3x+1\right)\left(20x-5\right)=-100\)

\(\Leftrightarrow60x^2+35x-\left(60x^2-15x+20x-5\right)=-100\)

\(\Leftrightarrow60x^2+35x-60x^2+15x-20x+5=-100\)

\(\Leftrightarrow30x=-100-5\)

\(\Leftrightarrow30x=-105\)

\(\Leftrightarrow x=\frac{-105}{30}=\frac{-7}{2}\)