a, (4x -1)(x-3)-(x-3)(5x+2) = 0
<=> (x-3)[(4x-1)-(5x+2)] = 0
<=> (x-3)(4x-1-5x-2) = 0
<=> (x-3)(-x-3)= 0
<=> \(\left[ \begin{array}{l}x-3=0\\-x-3=0\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=3\\x=-3\end{array} \right.\)
b, (x+6)(3x-1)+x²-36 = 0
<=> (x+6)(3x-1) + (x-6)(x+6) = 0
<=> (x+6)(3x-1+x-6) = 0
<=> (x+6)(4x-7)=0
<=> \(\left[ \begin{array}{l}x+6=0\\4x-7=0\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=-6\\x=\frac{7}{4}\end{array} \right.\)
c, (x+4)(5x-9)-x²+16 = 0
<=> (x+4)(5x-9)-(4-x)(4+x) = 0
<=> (x+4)(5x-9+4-x) = 0
<=> (x+4)(4x-5) = 0
<=> \(\left[ \begin{array}{l}x+4=0\\4x-5=0\end{array} \right.\)
<=> \(\left[ \begin{array}{l}x=-4\\x=\frac{5}{4} \end{array} \right.\)
