Question

(5x−6)2−(3x−7)2=−9x(x−8)+(5x−6)2−13

Answer 1

\(\left(5x-6\right)^2-\left(3x-7\right)^2=-9x\left(x-8\right)+\left(5x-6\right)^2-13\)

\(\Rightarrow25x^2-60x+36-9x^2+42x-49=-9x^2+72x+25x^2-60x+36-13\)

\(\Rightarrow\left(25x^2-25x^2\right)-\left(60x-60x\right)+\left(36-36\right)-\left(9x^2-9x^2\right)+\left(42x-72x\right)-\left(49-13\right)=0\)

\(\Rightarrow-30x-36=0\)

\(\Rightarrow-30x=36\)

\(\Rightarrow x=-\dfrac{36}{30}\)

\(\Rightarrow x=-\dfrac{6}{5}\)

Vậy: \(x=-\dfrac{6}{5}\)