If (a + b)² = 121 and ab = 10, then find a² + b².
Show answer & explanation
Correct answer: C
Explanation
Given:
(a + b)² = 121
ab = 10
By the formula:
(a + b)² = a² + b² + 2ab
121 = a² + b² + 2 × 10
121 = a² + b² + 20
a² + b² = 121 − 20
a² + b² = 101