Advanced Math practice question

Answer: -2 or −2

Take square roots of both sides, remembering both signs: x + 1 = 6 or x + 1 = −6. So x = 5 or x = −7, and the sum is 5 + (−7) = −2.

Common wrong answers

If you answered 5

5 is only the positive solution. x + 1 = −6 also works, giving x = −7.

If you answered 35

35 comes from dropping the square: x + 1 = 36. The equation says (x + 1)² = 36, so x + 1 = ±6.

If you answered -12

−12 is the sum of 6 and −6 with a sign slip, or −7 + (−5). The solutions are 5 and −7.

More Advanced Math questions

• Medium
  What are the solutions to x² − 5x + 6 = 0?
• Medium
  The graph of f(x) = (x − 3)² + 4 is a parabola. What are the coordinates of its vertex?
• Medium
  If x² − 2x − 8 = (x + 2)(x − a), what is the value of a?
• Medium
  If √(x + 5) = 4, what is the value of x?
• Medium
  If f(x) = x + 3 and g(x) = 2x, what is f(g(4))?
• Medium
  What are the solutions to x² + 6x + 8 = 0?