- #1

anemone

Gold Member

MHB

POTW Director

- 3,883

- 115

-----

Let $a$, $b$, $c$ and $d$ be real numbers with $a^2 + b^2 + c^2 + d^2 = 4$.

Prove that the inequality $(a+2)(b+2) \ge cd$ holds.

-----

Remember to read the https://mathhelpboards.com/showthread.php?772-Problem-of-the-Week-%28POTW%29-Procedure-and-Guidelines to find out how to https://mathhelpboards.com/forms.php?do=form&fid=2!