If x + y = 15 and xy = 14, then the value of x – y is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e 13.
| Understanding/Application |
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x + y = 15, xy = 14 (x + y)2 = 152 x2 + y2 + 2xy = 225 x2 + y2 + 2xy - 2xy + 2xy = 225 x2 + y2 + 4xy - 2xy = 225 |
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(x - y)2 + 4(14) = 225 (x - y)2 = 225 - 56 (x - y)2 = 169 (x - y) = 13 |