BD Merit - Freelancing, BCS, Bank, Primary, Admission, NTRCA

1 . x2+y2=25

A. 6
B. 7
C. 8
D. 9

View Answer

Discuss in Forum

Workspace

Report

Answer: Option B

Explanation:

দেওয়া আছে - x^{2} + y^{2} = 25 এবং xy = 12 {(x + y)}^{2} = x^{2} + 2 xy + y^{2} = x^{2} + y^{2} + 2 xy = 25 + 2.12 = 25 + 24 {(x + y)}^{2} = 49 x + y = 7

2 . x+y=7

A. 7
B. 25
C. 65
D. 91

View Answer

Discuss in Forum

Workspace

Report

Answer: Option D

Explanation:

দেওয়া আছে, x + y = 7 x^{2} + y^{2} = 25 \Rightarrow {(x + y)}^{2} - 2 x y = 25 \Rightarrow 7^{2} - 25 = 2 x y \Rightarrow 2 x y = 49 - 25 \Rightarrow x y = \frac{24}{2} = 12 x^{3} + y^{3} = {(x + y)}^{3} - 3 x y (x + y) = 7^{3} - 3 \times 12 \times 7 = 343 - 252 = 91