Class 10 Math All topics Quadratic Equations

If $3x−7y=10$ and $xy=−1$ then value of $9x_{2}+49y_{2}$ is?

Solution:

$9x_{2}+49y_{2}=(3x)_{2}+(7y)_{2}$

$⇒(3x+7y)_{2}−2×3x×7y$

or $(3x+7y)_{2}−2×3x×7y=(3x−7y)_{2}−2×3x×7y+4×3x×7y$

$⇒(3x−7y)_{2}+2×3x×7y$

$=(3x−7y)_{2}+42xy$

Given, $(3x−7y)=10$ & $xy=−1$

$∴9x_{2}+49y_{2}=10_{2}+42×(−1)=58$.

Similar topics

introduction to trigonometry

functions

some applications of trigonometry

quadratic equations

polynomials

introduction to trigonometry

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