(4x+5)(x=3)

Solution for (4x+5)(x=3) equation:

(4x+5)(x=3)

We move all terms to the left:

(4x+5)(x-(3))=0

We multiply parentheses ..

(+4x^2-12x+5x-15)=0

We get rid of parentheses

4x^2-12x+5x-15=0

We add all the numbers together, and all the variables

4x^2-7x-15=0

a = 4; b = -7; c = -15;
Δ = b2-4ac
Δ = -72-4·4·(-15)
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-17}{2*4}=\frac{-10}{8}
=-1+1/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+17}{2*4}=\frac{24}{8}
=3
$