A) 180
B) 144
C) 324
D) 170
Correct Answer: A
Solution :
We have, \[3x+4y=18~\] ?(i) \[xy=6~\] ?(ii) Squaring both sides of (i), we get \[{{(3x)}^{2}}+{{(4y)}^{2}}+2\times 3x\times 4y={{(18)}^{2}}\] \[=9{{x}^{2}}+16{{y}^{2}}+24xy=324\] \[9{{x}^{2}}+16{{y}^{2}}+24(6)=324\] (Using (ii)) \[9{{x}^{2}}+16{{y}^{2}}+144=324\] \[\Rightarrow 9{{x}^{2}}+16{{y}^{2}}=180\]You need to login to perform this action.
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