Discuss Forum
1. if x+y=7 and x^2+y^2 =25 then which of the following equals the value of x^3+y^3 ?
- A. 7
- B. 7
- C. 7
- D. 7
Answer: Option D
Explanation:
x + y = 7
x2 + y2 = 25
x2 + y2 = 25
(x + y)2 - 2xy = 25
7x2 - 2xy = 25
2xy = 24
xy = 12
x3 + y3 = ( x + y)3 - 3xy ( x + y)
= 73 - 3×12×7
= 343 - 252
= 91
Post your comments here: