x2=5(x+280)

Solution for x2=5(x+280) equation:

x2=5(x+280)

We move all terms to the left:

x2-(5(x+280))=0

We add all the numbers together, and all the variables

x^2-(5(x+280))=0


We calculate terms in parentheses: -(5(x+280)), so:

5(x+280)

We multiply parentheses

5x+1400

Back to the equation:

-(5x+1400)


We get rid of parentheses

x^2-5x-1400=0

a = 1; b = -5; c = -1400;
Δ = b2-4ac
Δ = -52-4·1·(-1400)
Δ = 5625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5625}=75$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-75}{2*1}=\frac{-70}{2}
=-35
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+75}{2*1}=\frac{80}{2}
=40
$