0=3x(5x-7)

Solution for 0=3x(5x-7) equation:

0=3x(5x-7)

We move all terms to the left:

0-(3x(5x-7))=0

We add all the numbers together, and all the variables

-(3x(5x-7))=0


We calculate terms in parentheses: -(3x(5x-7)), so:

3x(5x-7)

We multiply parentheses

15x^2-21x

Back to the equation:

-(15x^2-21x)


We get rid of parentheses

-15x^2+21x=0

a = -15; b = 21; c = 0;
Δ = b2-4ac
Δ = 212-4·(-15)·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-21}{2*-15}=\frac{-42}{-30}
=1+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+21}{2*-15}=\frac{0}{-30}
=0
$