If √a + √b = 12 and √a - √b = 4, then what is the value of a + b?
Show answer & explanation
Correct answer: C
Explanation
Given:
√a + √b = 12
√a − √b = 4
According to the formula:
(x + y)² + (x − y)² = 2(x² + y²)
(√a + √b)² + (√a − √b)²
= 12² + 4²
= 144 + 16
= 160
160 = 2(a + b)
a + b = 160 / 2
= 80