Squaring a binominal

Question

I have a really simple question that I can't find the answer to. In a algebra test, I was asked to simplify $(5 + $$\sqrt{3}$)$^2$. What I did was to square each term individually:

$5^2$+$\sqrt{3}$$^2$

I got

$25 + 3$ = $28$

This however was the wrong answer. Was there a problem with squaring the binominal? Thanks!

Ps, This was their answer:

$28+10\sqrt{3}$

Answer 1

$(5+\sqrt{3})^2=(5+\sqrt{3})(5+\sqrt{3})$ then FOIL.

Answer 2

$$(a+b)^2=a^2+2ab+b^2$$

You forget the term $2ab=2\times 5\times \sqrt{3}=10\times \sqrt{3}$

Answer 3

HINT: $$(a+b)^2=a^2+2ab+b^2$$ where $a=5$ and $b=\sqrt {3}$