Question

Use FOIL to solve this equation:


`5x^(2) -10= x^(2) +90`

Answer 1

FOIL is not for solving equations; it's for expanding the products of binomials.

5x^2 - 10 = x^2 + 90 becomes 4x^2 = 100, or x^2 = 25, so that x = plus or minus 5.