(42.7-x)*x=121

Solution for (42.7-x)*x=121 equation:

(42.7-x)*x=121

We move all terms to the left:

(42.7-x)*x-(121)=0

We add all the numbers together, and all the variables

(-1x+42.7)*x-121=0

We multiply parentheses

-1x^2+42.7x-121=0

a = -1; b = 42.7; c = -121;
Δ = b2-4ac
Δ = 42.72-4·(-1)·(-121)
Δ = 1339.29
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{-(42.7)-\sqrt{1339.29}}{2*-1}=\frac{-42.7-\sqrt{1339.29}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(42.7)+\sqrt{1339.29}}{2*-1}=\frac{-42.7+\sqrt{1339.29}}{-2}
$