First slide

Theory of equations

Question

If $x^{2} + y^{2} = 25, xy = 12, then x =$

Moderate

A

{3,4}
B

{3, -3}
C

{3, 4, -3, -4}
D

{-3, -3}

Solution

$x^{2} + y^{2} = 25 and xy = 12 \Rightarrow x^{2} + {(\frac{12}{x})}^{2} = 25 \Rightarrow x^{4} + 144 - 25 x^{2} = 0 \Rightarrow (x^{2} - 16) (x^{2} - 9) = 0^{} \Rightarrow x^{2} = 16 and x^{2} = 9 \Rightarrow x = \pm 4 and x = \pm 3$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App