SOLUTION: Solve and check 2x^2+7x=9 x=?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Solve and check 2x^2+7x=9 x=?      Log On


   

Question 715227: Solve and check
2x^2+7x=9
x=?
Answer by Simnepi(216) About Me  (Show Source):
You can put this solution on YOUR website!
let's get this into shape!
rearranging the equation gives 2x%5E2%2B7x-9=0
Now we look for factor pairs of the constant term i.e. 9
the factor pairs of -9 are
plus/minus 3 and plus minus 3
plus/minus 1 and plus/minus 9
given that the squared term coefficient is 2 and we have to add these factors to make the linear term's coefficient
the factor pair we will use is plus/minus 1 and plus/minus 9
because +9 + 2(-1) = +7
giving us
(2x+9)(x-1)=0
either of these could =0
so we have
2x+9=0 OR x-1=0
giving us
x=-9%2F2 OR x=1
CHECK
2%28-9%2F2%29%5E2%2B7%28-9%2F2%29=162%2F4-63%2F2=9
OR
2%281%29%5E2%2B7%281%29=9
both our solutions are correct!