84=2x^2-10x+3x-15

Solution for 84=2x^2-10x+3x-15 equation:

84=2x^2-10x+3x-15

We move all terms to the left:

84-(2x^2-10x+3x-15)=0

We get rid of parentheses

-2x^2+10x-3x+15+84=0

We add all the numbers together, and all the variables

-2x^2+7x+99=0

a = -2; b = 7; c = +99;
Δ = b2-4ac
Δ = 72-4·(-2)·99
Δ = 841
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{841}=29$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-29}{2*-2}=\frac{-36}{-4}
=+9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+29}{2*-2}=\frac{22}{-4}
=-5+1/2
$