x(5-2x)+15=3

Solution for x(5-2x)+15=3 equation:

x(5-2x)+15=3

We move all terms to the left:

x(5-2x)+15-(3)=0

We add all the numbers together, and all the variables

x(-2x+5)+15-3=0

We add all the numbers together, and all the variables

x(-2x+5)+12=0

We multiply parentheses

-2x^2+5x+12=0

a = -2; b = 5; c = +12;
Δ = b2-4ac
Δ = 52-4·(-2)·12
Δ = 121
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{121}=11$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-11}{2*-2}=\frac{-16}{-4}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+11}{2*-2}=\frac{6}{-4}
=-1+1/2
$