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Algebraic Expressions — MATHS STD 7 — Question

Gujarat BoardEnglish MediumSTD 7MATHSAlgebraic Expressions5 Marks
Question
How much does $a^2-3 a b+2 b^2$ exceed $2 a^2-7 a b+9 b^2 ?$
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Answer

Required expression:
$=\left(a^2-3 a b+2 b^2\right)-\left(2 a^2-7 a b+9 b^2\right)$
$=a^2-3 a b+2 b^2-2 a^2+7 a b-9 b^2$
Collecting positive and negative like terms together, we get
$=a^2-2 a^2-3 a b+7 a b+2 b^2-9 b^2$
$=-a^2+4 a b-7 b^2$

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