Question

Solve 2x^2-21x-36=0

Answer 1

$2x^2-21x-36=0$ 

$x_{1,\:2}=\dfrac{-b\pm \sqrt{b^2-4ac}}{2a}$ 

$\mathrm{For\:}\quad a=2,\:b=-21,\:c=-36:\quad x_{1,\:2}=\frac{-\left(-21\right)\pm \sqrt{\left(-21\right)^2-4\cdot \:2\left(-36\right)}}{2\cdot \:2}$ 

$x=\dfrac{-\left(-21\right)+\sqrt{\left(-21\right)^2-4\cdot \:2\left(-36\right)}}{2\cdot \:2}:\quad 12$ 

$x=\dfrac{-\left(-21\right)-\sqrt{\left(-21\right)^2-4\cdot \:2\left(-36\right)}}{2\cdot \:2}:\quad -\dfrac{3}{2}$ 

$x=12,\:x=-\dfrac{3}{2}$

Answer 2

The answer is B. Hope that help.