4=5. Refer to the following and find the mistake!!!!!!!!!!!!!!!!!!?

Question

-20 = -20
implies -36+16= -45+25
add 81/4 to both sides
-36+16+81/4 = -45+25+81/4
or [4-9/2]whole square = [5-9/2] whole square
or 4-9/2 =5-9/2
4 = 5
FIND THE FLAW!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Answer 1

instead of
4-9/2 =5-9/2
it should be
(-1/2)^2=1/2)^2

that is sqrt(x^2)=|x|
it is not x only it can be -x

Answer 2

whenever you square root both sides of an equation in the solving process, you need plus or minus. You should have had:

4-9/2 = 5-9/2 OR 4-9/2 = -(5-9/2).

The second statement is true, but the first must be discarded.

Answer 3

The flaw is that when you take the square root of both sides you don't allow for the possibilty of a negative solution, which the LHS was before you squared it.

Answer 4

is that 8 and 1/4 or eighty-one over 4?