Answer:
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Step-by-step explanation:
The first step is to find the GCF. Here, it's 3.
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Then, you factor the polynomial in the parenthesis.
To find the factors, you will need to find 2 numbers that add to -7, and multiply to 10. -2 and -5 add to -7 and multiply to 10. Now, replace -7a with the factors.
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This of this polynomial as 2 problems.
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Then, factor again.
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Then, you keep the factors in parenthesis, and combine the numbers on the outside.
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Since, there are 2 of the same factor, you only need one.
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BUT REMEMBER!! In the very beginning, we had a 3 that we took out, we STILL need to add that to the final answer. The <u>final answer</u> is:
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Let the boat speed in still water be b.
Let the current speed be c.
The speed going upstream is 20/4 = 5 mph.
The speed going downstream is 32/4 = 8 mph.
b - c = 5 ........(1)
b + c = 8 .......(2)
Adding equations (1) and (2) we get:
2b = 13
b = 13/2 = 6.5
Plugging in the value for b into equation (1) we find c = 1.5.
The boat speed in still water is 6.5 mph and the current speed is 1.5 mph.
The answer is C.
This is because 7 must be greater than 12-g.
G cannot equal 5 and below because 12-5=7.
Therefore C is the only answer that works.
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