Posted by **Wenny** on Saturday, January 26, 2008 at 8:04pm.

What is wrong with the following proof. You must explain your answer in words.

a>3

3a>3(3)

3a-a^2>9-a^2

a(3-a)>(3-a)(3+a)

a>3+a

0>3

the problem with the proof is that the fourth step needs the sign to be reverse...but why?

i looked at step 3 and there is nothing negative to reverse the sigh for...

- Math -
**drwls**, Saturday, January 26, 2008 at 9:37pm
From the first statement, a must be a positive number. In fact, it must exceed 3. (This is very important later). The second and third statements are correct, since you are either multiplying by positive numbers or just factoring. The fourth statement is incorrect because 3-a is a negative number.The directon of the > sign must change.

## Answer this Question

## Related Questions

- Math - Please help me with this problem: A bourbon that is 51 proof is 25.5% ...
- college math - I posted this problem earlier, but I still can't figure it out. ...
- math - A bourbon that is 51-proof is 25.5% alcohol by volume while one that is ...
- geometry - Construction: The midpoint of a line segment can be constructed. ...
- communication - In general, thesis or central idea is supported by claims; ...
- Abstract Algebra - If 2^n>n^2 and n>5, then 2^n+1>(n+1)^2 Proof: ...
- Philosophy - I need help with this proof for my philosophy class. This proof is ...
- geometry - Give the reason for the step taken from a proof. <1 and <2 are ...
- informal Logic - God must exist for there can be no other explanation for the ...
- Philosophy - I need help with this proof for my philosophy class. This proof is ...

More Related Questions