If ab=21, then $$\frac{(a+b)^2}{(a-b)^2}=\frac{25}{4}$$ then $$a^2+b^2+3ab$$ the value isÂ
Given : $$\frac{(a+b)^2}{(a-b)^2}=\frac{25}{4}$$
=> $$\frac{a^2+b^2+2ab}{a^2+b^2-2ab}=\frac{25}{4}$$
Let $$(a^2+b^2)=x$$ and $$ab=21$$
=> $$\frac{x+42}{x-42}=\frac{25}{4}$$
=> $$4x+(42 \times 4)=25x-(42 \times 25)$$
=> $$25x-4x=(42 \times 4)+(42 \times 25)$$
=> $$21x=42 \times (4+25)$$
=> $$x=\frac{42 \times 29}{21}$$
=> $$x=2 \times 29=58$$
$$\therefore$$Â $$a^2+b^2+3ab$$
= $$58+3(21)$$
= $$58+63=121$$
=> Ans - (B)
Create a FREE account and get: