Difference between revisions of "2020 IMO Problems/Problem 2"
m (→Solution) |
m (→Solution) |
||
Line 8: | Line 8: | ||
Using Weighted AM-GM we get | Using Weighted AM-GM we get | ||
− | <cmath>\frac{a | + | <cmath>\frac{a\cdot a +b\cdot b +c\cdot c +d\cdot d}{a+b+c+d} \ge \sqrt[a+b+c+d]{a^a b^b c^c d^d}</cmath> |
<cmath>\implies a^a b^b c^c d^d \le a^2 +b^2 +c^2 +d^2</cmath> | <cmath>\implies a^a b^b c^c d^d \le a^2 +b^2 +c^2 +d^2</cmath> |
Revision as of 19:52, 27 September 2020
Problem 2. The real numbers are such that and . Prove that
Solution
Using Weighted AM-GM we get
So,
Now notice that
So, we get
Now, for equality we must have
In that case we get
~ftheftics