x=(7x)(3x-20)

Solution for x=(7x)(3x-20) equation:

x=(7x)(3x-20)

We move all terms to the left:

x-((7x)(3x-20))=0


We calculate terms in parentheses: -(7x(3x-20)), so:

7x(3x-20)

We multiply parentheses

21x^2-140x

Back to the equation:

-(21x^2-140x)


We get rid of parentheses

-21x^2+x+140x=0

We add all the numbers together, and all the variables

-21x^2+141x=0

a = -21; b = 141; c = 0;
Δ = b2-4ac
Δ = 1412-4·(-21)·0
Δ = 19881
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{19881}=141$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(141)-141}{2*-21}=\frac{-282}{-42}
=6+5/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(141)+141}{2*-21}=\frac{0}{-42}
=0
$