\(\left(5x-3\right)^2-\left(4x-7\right)^2=49\)
\(\Rightarrow\left(5x-3-4x+7\right)\left(5x-3+4x-7\right)-49=0\)
\(\Rightarrow\left(x+4\right)\left(9x-10\right)-49=0\)
\(\Rightarrow9x^2-10x+36x-40-49=0\)
\(\Rightarrow9x^2-26x-89=0\)
\(\Rightarrow...\)