The sum of two numbers is 7 and the sum of their cubes is 133, find the sum of their square. Let a, b be the two numbers. ⇒ (7)3 = 133 + 3ab (7)⇒ 343 = 133 + 21ab⇒ 21ab = 343 - 133 = 210⇒ 21ab = 210 ⇒ ab= 10 Now a2 + b2 = (a + b)2 - 2ab Concept: Expansion of Formula Is there an error in this question or solution? |