Question
If x= - and y= + , then which one of the following is correct ?
NDA
Mathematics
Trigonometric Ratios & Identities
2026
NDA 2026 (Phase 1)
NDA Mathematics Question (2026) — Solution
Options
- A. x+y-xy-1=0
- B. x-y+xy+1=0
- C. x+y+xy-1=0
- D. x-y+xy-1=0
Answer
B. x-y+xy+1=0
Step-by-step solution
Given x = - = 1 - y = + = 1 + Consider x(y+1): x(y+1) = ( 1 - ) ( 1 + + 1 ) x(y+1) = ( 1 - ) ( 1 + + ) x(y+1) = 1 + + - - - ^2 x(y+1) = (1 - ^2 ) + - x(y+1) = ^2 + - x(y+1) = ( + 1 - ) x(y+1) = 1 + - x(y+1) = + - 1 Substituting y = + : x(y+1) = y - 1 xy + x - y + 1 = 0 Answer: x-y+xy+1=0
Related: Mathematics — Trigonometric Ratios & Identities · All PYQ Banks