Answer:
x = sqrt(15) - 1 or x = -1 - sqrt(15)
Explanation:
Solve for x:
x^2 + 2 x + 7 = 21
Subtract 7 from both sides:
x^2 + 2 x = 14
Add 1 to both sides:
x^2 + 2 x + 1 = 15
Write the left hand side as a square:
(x + 1)^2 = 15
Take the square root of both sides:
x + 1 = sqrt(15) or x + 1 = -sqrt(15)
Subtract 1 from both sides:
x = sqrt(15) - 1 or x + 1 = -sqrt(15)
Subtract 1 from both sides:
Answer: x = sqrt(15) - 1 or x = -1 - sqrt(15)