gagangm wrote:
(4 - 5x)^2 = 1
For this to be 1,
x must be 1.
This will make both A and B equal to 1.
A: (4 - 5x) + (4 - 5x)^2
B: 1
(4 - 5x) + 1 = 5 - 5x
x = 1;
A will be 0.
So the answer will be B.
Other way is,
4 - 5x + 1 and 1
5 - 5x and 1
subtract -5 from both sides,
-5x and -4
divide both sides by 5,
-x/5 and -4/5
multiply both sides by 5
-x and -4
x and 4.
We know that x is equal to 1,
Therefore the answer is B again.
How is it D?
Its (4-5x) that we are concerned with. If you are confused just suppose y = (4-5x). This makes our the expression equivalent to y+y^2. So, we have y^2 = 1, which means y can be -1 and +1 as squaring -1 and +1 result in 1. Thus when y=1, y+y^2 = 2 but when y = -1, y+y^2 = 0. Thus, D is the answer.