Find the fourth proportional of (x4 - y4), (x + y) and (x - y), provided x ≠ y.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. (x2 + y2)-1.
Fourth proportion = [(x + y)(x - y)]/(x4 - y4)
= (x2 - y2)/(x4 - y4)
= 1/(x2 + y2)
= (x2 + y2)-1