Algebraic Identities — Maths STD 9 — Question

Given expression is $75 \times 75+2 \times 75 \times 25+25 \times 25$
Let $75=\mathrm{a}$ and $25=\mathrm{b}$
Then, we have
$a \times a+2 \times a \times b+b \times b$
$=a^2+2 a b+b^2$
$=(a+b)^2$
$=(75+25)^2$
$=(100)^2$
$=10000$
Hence, correct option is $(a)$.