15=5(1-m)(1-m)

Solution for 15=5(1-m)(1-m) equation:

15=5(1-m)(1-m)

We move all terms to the left:

15-(5(1-m)(1-m))=0

We add all the numbers together, and all the variables

-(5(-1m+1)(-1m+1))+15=0

We multiply parentheses ..

-(5(+m^2-1m-1m+1))+15=0


We calculate terms in parentheses: -(5(+m^2-1m-1m+1)), so:

5(+m^2-1m-1m+1)

We multiply parentheses

5m^2-5m-5m+5

We add all the numbers together, and all the variables

5m^2-10m+5

Back to the equation:

-(5m^2-10m+5)


We get rid of parentheses

-5m^2+10m-5+15=0

We add all the numbers together, and all the variables

-5m^2+10m+10=0

a = -5; b = 10; c = +10;
Δ = b2-4ac
Δ = 102-4·(-5)·10
Δ = 300
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{300}=\sqrt{100*3}=\sqrt{100}*\sqrt{3}=10\sqrt{3}$
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-10\sqrt{3}}{2*-5}=\frac{-10-10\sqrt{3}}{-10}
$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+10\sqrt{3}}{2*-5}=\frac{-10+10\sqrt{3}}{-10}
$