Question

What should be added to $3xy-4a^2+5b^2+2$ to get $-5+4a^2+2b^2-7xy$?

• A. $8a^2+3b^2-11xy+10$
• B. $-8a^2+3b^2+10xy+7$
• C. $-8a^2-3b^2+10xy+7$
• D. $8a^2+3b^2+10xy+7$

Answer 1

The correct option is B $-8a^2+3b^2+10xy+7$

Let the term to be added be 's' .
$3xy-4a^2+5b^2+2+s=-5+4a^2+2b^2-7xy$
$\Rightarrow s=(-5+4a^2+2b^2-7xy)-(3xy-4a^2+5b^2+2)$
Rearranging the terms and subtracting,
$-4a^2+5b^2+3xy+2$
$4a^2+2b^2-7xy-5$
(-) (-) (+) (+)
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$-8a^2+3b^2+10xy+7$