[Arctic Fox]

let X+Y=Z

multiply both sides by four:
4X+4Y=4Z

and by five:
5Z=5X+5Y

add the two:
4X+4Y+5Z=5X+5Y+4Z

subtract 9Z from each side:
4X+4Y-4Z=5X+5Y-5Z

thus:
4(X+Y-Z)=5(X+Y-Z)

divide both sides by (X+Y-Z):
4=5

[DougB]

...

[pooh]

When you get to 4(X+Y-Z)=5(X+Y-Z) you are multiplying 4 and zero which equals zero. 5 multiplied by zero is also zero....so what you have is 0=0 not 4=5

[skyguy79]

Does a cross-dressing mathematician wear an algebra?

[Arctic Fox]

Originally Posted by pooh

When you get to 4(X+Y-Z)=5(X+Y-Z) you are multiplying 4 and zero which equals zero. 5 multiplied by zero is also zero....so what you have is 0=0 not 4=5

Top of the class, Pooh :-)

[Uskesso]

Originally Posted by skyguy79

Does a cross-dressing mathematician car parts wear an algebra?

Worst knowledge of algebra. Must not become maths teacher