15=(1+0.05x)*(4000-80x)

Solution for 15=(1+0.05x)*(4000-80x) equation:

15=(1+0.05x)(4000-80x)

We move all terms to the left:

15-((1+0.05x)(4000-80x))=0

We add all the numbers together, and all the variables

-((0.05x+1)(-80x+4000))+15=0

We multiply parentheses ..

-((+0x^2+0x-80x+4000))+15=0


We calculate terms in parentheses: -((+0x^2+0x-80x+4000)), so:

(+0x^2+0x-80x+4000)

We get rid of parentheses

0x^2+0x-80x+4000

We add all the numbers together, and all the variables

x^2-79x+4000

Back to the equation:

-(x^2-79x+4000)


We get rid of parentheses

-x^2+79x-4000+15=0

We add all the numbers together, and all the variables

-1x^2+79x-3985=0

a = -1; b = 79; c = -3985;
Δ = b2-4ac
Δ = 792-4·(-1)·(-3985)
Δ = -9699
Delta is less than zero, so there is no solution for the equation