-x2=21x+98

Solution for -x2=21x+98 equation:

-x2=21x+98

We move all terms to the left:

-x2-(21x+98)=0

We add all the numbers together, and all the variables

-1x^2-(21x+98)=0

We get rid of parentheses

-1x^2-21x-98=0

a = -1; b = -21; c = -98;
Δ = b2-4ac
Δ = -212-4·(-1)·(-98)
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-7}{2*-1}=\frac{14}{-2}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+7}{2*-1}=\frac{28}{-2}
=-14
$