-18=15-3x(6x+5)

Solution for -18=15-3x(6x+5) equation:

-18=15-3x(6x+5)

We move all terms to the left:

-18-(15-3x(6x+5))=0


We calculate terms in parentheses: -(15-3x(6x+5)), so:

15-3x(6x+5)

determiningTheFunctionDomain
-3x(6x+5)+15

We multiply parentheses

-18x^2-15x+15

Back to the equation:

-(-18x^2-15x+15)


We get rid of parentheses

18x^2+15x-15-18=0

We add all the numbers together, and all the variables

18x^2+15x-33=0

a = 18; b = 15; c = -33;
Δ = b2-4ac
Δ = 152-4·18·(-33)
Δ = 2601
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2601}=51$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-51}{2*18}=\frac{-66}{36}
=-1+5/6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+51}{2*18}=\frac{36}{36}
=1
$