\(a,\left(x+8\right)^2-\left(3x-7\right)^2=0\\ \Leftrightarrow\left(x+8-3x+7\right)\left(x+8+3x-7\right)=0\\ \Leftrightarrow\left(-2x+15\right)\left(4x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{15}{2}\\x=-\dfrac{1}{4}\end{matrix}\right.\)
\(b,\left(x-5\right)\left(x+6\right)-\left(x-5\right)^2=0\\ \Leftrightarrow\left(x-5\right)\left(x+6-x+5\right)=0\\ \Leftrightarrow11\left(x-5\right)=0\\ \Leftrightarrow x-5=0\\ \Leftrightarrow x=5\)
\(c,\left(x+7\right)\left(x+8\right)-\left(x-3\right)^2=0\\ \Leftrightarrow x^2+15x+56-x^2+6x-9=0\\ \Leftrightarrow21x+47=0\\ \Leftrightarrow x=\dfrac{-47}{21}\)
caau d nghiệm xấu lắm đề có đúng không bạn
