Question
If $a-b=5$ and $a b=12$, find the value of $a^2+b^2$.

Answer

We have to find the value $a^2+b^2$
Given $a - b =5, ab =12$
Using identity $(a-b)^2=a^2-2 a b+b^2$
By substituting the value of $a-b=5, a b=12$ we get,
$(5)^2=a^2+b^2-2 \times 12$
$5 \times 5=a^2+b^2-2 \times 12$
By transposing -24 to left hand side we get
$25+24=a^2+b^2$
$49=a^2+b^2$
Hence the value of $a^2+b^2$ is 49 .

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