0=3(x2+7x-15)

Solution for 0=3(x2+7x-15) equation:

0=3(x2+7x-15)

We move all terms to the left:

0-(3(x2+7x-15))=0

We add all the numbers together, and all the variables

-(3(+x^2+7x-15))+0=0

We add all the numbers together, and all the variables

-(3(+x^2+7x-15))=0


We calculate terms in parentheses: -(3(+x^2+7x-15)), so:

3(+x^2+7x-15)

We multiply parentheses

3x^2+21x-45

Back to the equation:

-(3x^2+21x-45)


We get rid of parentheses

-3x^2-21x+45=0

a = -3; b = -21; c = +45;
Δ = b2-4ac
Δ = -212-4·(-3)·45
Δ = 981
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{981}=\sqrt{9*109}=\sqrt{9}*\sqrt{109}=3\sqrt{109}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-3\sqrt{109}}{2*-3}=\frac{21-3\sqrt{109}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+3\sqrt{109}}{2*-3}=\frac{21+3\sqrt{109}}{-6}
$