Q.The fourth proportional of ( ???? 2 − ???? ???? + ???? 2 ) , ( ???? 3 + ???? 3 ) , and ( ???? − ???? ) is (a) \(x^2+y^2\) (b) \(x+y\) (c) \(x^2-y^2\) (d) \(x-y\)
Answer: C
Let the fourth proportional be \(p\) \(\therefore \frac{(x^2 - xy + y^2)}{(x^3 + y^3)} = \frac{(x - y)}{p}\) ⇒ \(p(x^2 - xy + y^2) = (x - y)(x^3 + y^3)\) ⇒ \(p = \frac{(x - y)(x^3 + y^3)}{(x^2 - xy + y^2)}\)     \(= \frac{(x - y)(x + y)\cancel{(x^2 - xy + y^2)}}{\cancel{(x^2 - xy + y^2)}}\)     \(= x^2 - y^2\)
Similar Questions