3x*x+5x*x=400x

Solution for 3x*x+5x*x=400x equation:

3x*x+5x*x=400x

We move all terms to the left:

3x*x+5x*x-(400x)=0

We add all the numbers together, and all the variables

-400x+3x*x+5x*x=0

Wy multiply elements

3x^2+5x^2-400x=0

We add all the numbers together, and all the variables

8x^2-400x=0

a = 8; b = -400; c = 0;
Δ = b2-4ac
Δ = -4002-4·8·0
Δ = 160000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{160000}=400$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-400)-400}{2*8}=\frac{0}{16}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-400)+400}{2*8}=\frac{800}{16}
=50
$