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Re: (4 – 5x)^2 = 1 [#permalink]
1
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.
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Re: (4 – 5x)^2 = 1 [#permalink]
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