Answer:
x = 3 and x = -7
Step-by-step explanation:
The method I used is the x method, where you place the constant on the top and the coefficient of the second term on the bottom. From there, you find two numbers that multiply to get the top number (21) and add to give the bottom number (4).
You should get -3 and 7. You should be able to rewrite the equation as so:
(x - 3) (x + 7)
Set both equal to zero separately and solve:
x - 3 = 0
x = -3
x + 7 = 0
x = -7
