question_answer

If \[x+y-7=0\]and \[3x+y-13=0,\] then what is \[4{{x}^{2}}+{{y}^{2}}+4xy\] equal to?

A) 75                                

B) 85

C) 91                                

D) 100

Correct Answer: D

Solution :

\[\Rightarrow \]   x = 3 \[\therefore \] y = 4 Now, \[4{{x}^{2}}+ {{y}^{2}}+ 4xy\] \[=~~{{\left( 2x+ y \right)}^{2}}= {{\left( 2 {{x}^{3}}+ 4 \right)}^{2}}=100\]