Digital PSAT Math Practice Question 207: Answer and Explanation

Question: 207

If x > 0 and x² + 10x = 11, what is the value of x + 5?

Correct Answer: 6

Explanation:

(6) Look for a way to seamlessly make the original expression a variation on x + 5. Add 25 to both sides of the equation: x² + 10x = 11, and the result can be expressed as (x + 5)² = 36. Therefore, x + 5 = 6.

Alternatively, you could determine the value of x using the quadratic formula, , but this will be more labor-intensive than noticing the short-cut.