Question

To make $(x^4+4y^4)$ perfect square we have to substract-

• A. $4xy$
• B. $2y^2{x}^2$
• C. $2xy$
• D. $4y^2{x}^2$

Answer 1

Answer: (D)

$4y^2{x}^2$

To make $x^4+4y^3=4$ as $(a+b{)}^2$ or $(a-b{)}^2$ we need to add $4x^2{y}^2$ or substract $4x^2{y}^2$ , so according to the question we need to substract $4x^2{y}^2$ so , we get

$\therefore$ $x^4+4y^4-4x^2{y}^2=(x^2-2y^2{)}^2$

$\therefore$ The solution is $4y^2{x}^2$.