1.) 2z^2 - 7z + 5
2.) 9y^2 + 30yw + 25w^2
3.) 2x^2 - xy - 28y^2
4.) 72x^3y - 2xy^3
5.) 2u^4v^3 - 32v^3
+128460 a + b = -7 ⇒ b = -7 - a (1)
ab = -7 (2)
Sub (1) into (2)
a ( -7 - a) = -7
-7a - a^2 = -7 mutiply through by -1
a^2 + 7a = 7 complete the square on a
a^2 + 7a + 49/4 = 7 + 49/4 factor the left side and simplify the right
(a + 7/2)^2 = 77/4 take the positive root
a + 7/2 = sqrt (77) / 2
a = sqrt (77)/2 - 7/2
b = -7 - a = -7 - ( sqrt (77/2) - 7/2) = -sqrt (77) / 2 - 7/2
