Solve $LaTeX: \displaystyle 3 x^{2} - 9 x - 84=0$

Since the GCF is $LaTeX: \displaystyle 3$ we need we factor out the GCF to get $LaTeX: \displaystyle 3(x^{2} - 3 x - 28)$ . This is now a pq method factoring. The factors of $LaTeX: \displaystyle -28$ that add up to $LaTeX: \displaystyle -3$ are $LaTeX: \displaystyle 4$ and $LaTeX: \displaystyle -7$ . This gives $LaTeX: \displaystyle 3(x + 4)(x - 7)=0$ . The solutions are $LaTeX: \displaystyle x = -4$ and $LaTeX: \displaystyle x = 7$