Math Is Fun Forum

simone

Member

Registered: 2007-10-05

Posts: 19

simplifying expressions

Please someone help me out!!!

I'm not able to simplify this expression:

(sqrt(9+sqrt(80)) + sqrt(9-sqrt(80)))^2

The result posted on the textbook I'm practicing on is 20, but I cannot get to it.

Thank you guys, the forum rocks!

saudi_boy

Member

Registered: 2006-11-01

Posts: 41

Re: simplifying expressions

apply

we get

then simplify

apply

we'll get

finally

simone

Member

Registered: 2007-10-05

Posts: 19

Re: simplifying expressions

thank you so much. could you please also help me work this problem out?

The equation

|x/2| + |y/2| = 5

encloses a certain region on a coordinate plane. What is the area of this region?

thank you.

Identity

Member

Registered: 2007-04-18

Posts: 934

Re: simplifying expressions

There are 4 different possibilites:
1. x/2 is positive and y/2 is positive,
2. they are both negative,
3. one is positive and the other is negative,
4. the other is positive and one is negative.

Solve each of those four cases to find the lines enclosing the region. I will do 1 and 3:

1.

3.

Find 2. and 4. then graph the lines. Finding the area of the region should follow from the diagram rather easily. (If the area is funny-looking, split it up into smaller shapes which you can easily find the area of).

This is how you are supposed to do it, I'm sure of that, but why? I'm still thinking.

Wouldn't mind if someone could help explain "WHY!"? But no, really, I don't exactly understand the reasoning behind it.

Last edited by Identity (2007-10-06 02:02:50)