2/5x-3/4x=20

Solution for 2/5x-3/4x=20 equation:

2/5x-3/4x=20

We move all terms to the left:

2/5x-3/4x-(20)=0


Domain of the equation: 5x!=0

x!=0/5

x!=0

x∈R



Domain of the equation: 4x!=0

x!=0/4

x!=0

x∈R


We calculate fractions


8x/20x^2+(-15x)/20x^2-20=0

We multiply all the terms by the denominator


8x+(-15x)-20*20x^2=0

Wy multiply elements

-400x^2+8x+(-15x)=0

We get rid of parentheses

-400x^2+8x-15x=0

We add all the numbers together, and all the variables

-400x^2-7x=0

a = -400; b = -7; c = 0;
Δ = b2-4ac
Δ = -72-4·(-400)·0
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-7}{2*-400}=\frac{0}{-800}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+7}{2*-400}=\frac{14}{-800}
=-7/400
$