40=x^2-14x

Solution for 40=x^2-14x equation:

40=x^2-14x

We move all terms to the left:

40-(x^2-14x)=0

We get rid of parentheses

-x^2+14x+40=0

We add all the numbers together, and all the variables

-1x^2+14x+40=0

a = -1; b = 14; c = +40;
Δ = b2-4ac
Δ = 142-4·(-1)·40
Δ = 356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{356}=\sqrt{4*89}=\sqrt{4}*\sqrt{89}=2\sqrt{89}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-2\sqrt{89}}{2*-1}=\frac{-14-2\sqrt{89}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+2\sqrt{89}}{2*-1}=\frac{-14+2\sqrt{89}}{-2}
$