What are we going to do without Shiningsunnyday?!?
by SantaDragon, Apr 29, 2016, 7:47 AM
OH NO! Shiningsunnyday has died! What are we going to do?!?
Shiningsunnyday may be gone
Cough, um anyway.
As some of you may know, Shiningsunnyday has appointed me as a contributor to his blog. So now let's begin with some math shall we?
First, let us introduce one of the most fundamentals
The Trivial Inequality:
for all real numbers
.
Now obviously, an inequality problem never screams to us "Hey it's me! Look I'm an
!", we have to use some cleverness and manipulations first in order to prove our inequalities.
A final note about inequality problems: When asked to prove that a certain inequality is true, you can think backwards but write your solution forwards. That is, you can go from said inequality and work your way backwards to a true statement, but just be sure that all your steps are reversible and that write your proof beginning with you true statement.
A Classic Problem:
Prove:
Motivation+Solution
Another Problem:
Prove
(Source: Intermediate Algebra)
Solution
Hope y'all liked the problems!
Shiningsunnyday may be gone
although he'll probably be ressurrected
... but his dream, a USAMO dream... must live on. And I shall carry the ember of his dream, and it shall ignite into a bonfire! For this USAMO dream must live on!Cough, um anyway.
As some of you may know, Shiningsunnyday has appointed me as a contributor to his blog. So now let's begin with some math shall we?
First, let us introduce one of the most fundamentals
“These guys don’t practice the fundamentals, you know.”- Uncle Drew (aka Kyrie Irving)
of inequalities.The Trivial Inequality:


Now obviously, an inequality problem never screams to us "Hey it's me! Look I'm an

A final note about inequality problems: When asked to prove that a certain inequality is true, you can think backwards but write your solution forwards. That is, you can go from said inequality and work your way backwards to a true statement, but just be sure that all your steps are reversible and that write your proof beginning with you true statement.
A Classic Problem:
Prove:

Motivation+Solution
Motivation: Hm, we are seeing a lot of symmetry here.
and
,
,
, and
. This should remind of of some expressions in which we square
or
.
Solution:

we can subtract both sides by
and multplying by 2 yields:

Now we see where we can use the trivial inequality! Separate this as:


Which is true since each piece is true by the trivial inequality.
Remember to write your solutions forward.







Solution:

we can subtract both sides by


Now we see where we can use the trivial inequality! Separate this as:


Which is true since each piece is true by the trivial inequality.
Remember to write your solutions forward.
Another Problem:
Prove

Solution
Hm. This one isn't so obvious. Let's first move everything to one side.

Well, we can group the
, and that's a square, but what about the other terms?
...
AHA. Do you see the square?

If we let
, this becomes more clear.


Which is a square. Now, we just write our proof forwards.

Well, we can group the

...
AHA. Do you see the square?

If we let



Which is a square. Now, we just write our proof forwards.
Hope y'all liked the problems!