(15x-21)*(x=63)

Solution for (15x-21)*(x=63) equation:

(15x-21)(x=63)

We move all terms to the left:

(15x-21)(x-(63))=0

We multiply parentheses ..

(+15x^2-945x-21x+1323)=0

We get rid of parentheses

15x^2-945x-21x+1323=0

We add all the numbers together, and all the variables

15x^2-966x+1323=0

a = 15; b = -966; c = +1323;
Δ = b2-4ac
Δ = -9662-4·15·1323
Δ = 853776
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{853776}=924$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-966)-924}{2*15}=\frac{42}{30}
=1+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-966)+924}{2*15}=\frac{1890}{30}
=63
$