4x-7.2=3x(x+5)

Solution for 4x-7.2=3x(x+5) equation:

4x-7.2=3x(x+5)

We move all terms to the left:

4x-7.2-(3x(x+5))=0


We calculate terms in parentheses: -(3x(x+5)), so:

3x(x+5)

We multiply parentheses

3x^2+15x

Back to the equation:

-(3x^2+15x)


We get rid of parentheses

-3x^2+4x-15x-7.2=0

We add all the numbers together, and all the variables

-3x^2-11x-7.2=0

a = -3; b = -11; c = -7.2;
Δ = b2-4ac
Δ = -112-4·(-3)·(-7.2)
Δ = 34.6
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{-(-11)-\sqrt{34.6}}{2*-3}=\frac{11-\sqrt{34.6}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+\sqrt{34.6}}{2*-3}=\frac{11+\sqrt{34.6}}{-6}
$