Question

Solve 5x²+9x-12=0 by factoring

Answer 1

Answer:

  x = -3, 4/5

Step-by-step explanation:

To factor the equation, you need to find factors of (5)(-12) that have a sum of (+9).

  (5)(-12) = -60 = 60(-1) = 30(-2) = 15(-4) = 12(-5) = 10(-6)

The factors 15 and -4 have a sum of 9, so we can factor the equation as ...

  5x² +15x -4x -12 = 0

  5x(x +3) -4(x +3) = 0  . . . .  factor pairs of terms

  (5x -4)(x +3) = 0

The solutions are the values of x that make these factors zero:

  5x -4 = 0   ⇒   x = 4/5

  x +3 = 0   ⇒   x = -3

The solutions are x = -3 or 4/5.