Answer:
Step-by-step explanation:
1) If you really meant X^2+12=40, then this simplifies to x^2 = 28, and therefore x = ±√28, or x = ±2√7.
2) If you meant X^2+12x=40:
a) Take half of the coefficient of x: that would be (1/2)(12), or 6.
b) Square this result, obtaining: 6² = 36
c) Add this 36 to x^2 + 12x + 40, and then subtract it: We get:
x² + 12x + 36 - 36 = 40, or x² + 12x + 36 = 76
We have to add 36, as indicated above, to "complete the square."
