21x-98-x2=0

Solution for 21x-98-x2=0 equation:

21x-98-x2=0

We add all the numbers together, and all the variables

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