The correct option is D 3x+yx−3y
Given expression:9x2−y23x2−10xy+3y2
As 9x2−y2 and 3x2−10xy+3y2 are two algebraic expressions and are in the form of AB, 9x2−y23x2−10xy+3y2 is a rational algebraic expression.
Consider the numerator i.e. 9x2−y2
It can be written as (3x)2−(y)2
It is in the form of a2−b2
We know that a2−b2=(a−b)(a+b)
⇒(3x)2−(y)2=(3x−y)(3x+y)
Consider the denominator i.e. 3x2−10xy+3y2
3x2−10xy+3y2 can be written as
3x2−9xy−xy+3y2
⇒3x(x−3y)−y(x−3y)
⇒(3x−y)(x−3y)
Now, 9x2−y23x2−10xy+3y2=(3x−y)(3x+y)(3x−y)(x−3y)
=3x+yx−3y
∴9x2−y23x2−10xy+3y2=3x+yx−3y