Question 84
Find all real numbers $a, b, c, d$ such that
$$
a + b + c + d = 20
$$
and
$$
ab + ac + ad + bc + bd + cd = 150.
$$
$$
a + b + c + d = 20
$$
and
$$
ab + ac + ad + bc + bd + cd = 150.
$$
MathNet 2008-part-03 — 165 problems (EN–VI) Question 84
Math Olympiad Vault · MathNet 2008-part-03 — 165 problems (EN–VI)