Write an indirect proof for the following given 4y divided by6y 6 equals 20 prove y not equal to -1?

Answer 1

Assuming the given is written as:

4y/6y6=20

First off, this can be simplified down to:

2/3y5=20

Since this is an indirect proof, we must first assume the opposite of what you are trying to prove. You are trying to prove that y is not equal to -1.

Let y=-1

If this was done, then the following substitution would be made:

2/3(-1)5=20

2/3(-1)=20

2/(-3)=20

-2/3 =20

Clearly, -2/3 does not equal 20. Since y=-1 causes a mathematically impossible statement, then y cannot equal -1.

As far as formatting it for a formal indirect proof, I'm no help there. Different teachers like different formatting.