Consider this quadratic equation

X^2+2x+7=21

x = sqrt (15) - 1 or x = - 1 - sqrt (15)

Step-by-step 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)