Solve the equation (4m-2)^2 - 2(4m-2)=15.

Question

lgbasallote · Answer

expand first $$\implies (16m^2 - 16m + 4) - (8m - 4) = 15$$
simplify
$$\implies 16m^2 - 16m + 4 - 8m + 4 = 15$$
combine like terms
$$\implies 16m^2 -24m + 8 = 15$$
subtract 15 from both sides
$$\implies 16m^2 - 24m - 7 = 0$$
use quadratic formula to solve for m

anonymous · Answer

Thanks you sir, I was stuck on that problem for 10 mins and i forgot to overlook factoring (4m-2)(4m-2).

lgbasallote · Answer

no worries. glad to help you out of the stump

callisto · Answer

A little bit late.
But I did it in this way.
 (4m-2)^2 - 2(4m-2)=15
 (4m-2)^2 - 2(4m-2) - 15=15 - 15
 (4m-2)^2 - 2(4m-2)-15 = 0
Just consider (4m-2) as x, you'll get.
x^2 - 2x -15 = 0 
(x-5)(x+3) = 0
x= 5     or       x=-3
Put back x=4m-2 into the solutions you got.
4m-2 = 5  or    4m-2 = -3  <- solve these two equations.

If you understand how to do it, you can skip the step of letting x=4m-2...