Answer: 
The expression is in the form 
where a = -25 and b = 18
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Work Shown:
Let 
and then square both sides
We'll use both x and x^2 later on.
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The denominator is in the form 4+x. We'll multiply top and bottom by 4-x to then use the difference of squares rule. This will allow us to eliminate the square root in the denominator.
Therefore,
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Checking the answer:
Use a calculator to find that,
We get the same decimal approximation, which helps confirm the correct answer.
Or you could use the idea that if M = N, then M-N = 0 to subtract the original expression M and the final result N. You should get 0 or very close to it.
A line perpendicular to another occurs at the negative reciprocal of the slope of the original line. Why this is, I can further explain in the comments if you're interested. What is a reciprocal though? a reciprocal, if you're unfamiliar, is just the flipped form of it.
As an example, the negative reciprocal of 1/4 is -4/1. I multiplied 1/4 by a negative, and flipped the fraction.
So, what would the negative reciprocal of 3 be? well, you can imagine 3 to be 3/1 to help. so we multiply it by a negative, which gives us -3/1, and then we flip it, giving us -1/3. This is the slope of our unknown line. Because of this, we can mark out...well all of them haha. You need to double check your question and answers provided. With the info you've given me, none of your answers are correct. Let me know what happened if you can! if not, I would question your teacher, cause they messed up somewhere haha.
15.40 + 8.50l (l is variable for labor)
8.50 x 2.5 = 21.25
15.40 + 21.25 = 36.65.
That is the answer for A.
504.20 - 15.40 = 488.80
488.80 / 8.50 = <span>57.50
About 57.50 hours for B.</span>
