12-7x(x=3)

Solution for 12-7x(x=3) equation:

12-7x(x=3)

We move all terms to the left:

12-7x(x-(3))=0

We multiply parentheses

-7x^2+21x+12=0

a = -7; b = 21; c = +12;
Δ = b2-4ac
Δ = 212-4·(-7)·12
Δ = 777
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-\sqrt{777}}{2*-7}=\frac{-21-\sqrt{777}}{-14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{777}}{2*-7}=\frac{-21+\sqrt{777}}{-14}
$