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Jesse is traveling up and down a stream in a kayak. He can paddle the kayak at an average rate of 5 miles/hour, and the round-trip is a total distance of 16 miles. When [tex]c[/tex] is the speed of the current, this expression can be used to find the difference in the time it takes Jesse to travel upstream (against the current) and downstream (with the current).

[tex]\[ \frac{8}{5-c} - \frac{8}{5+c} \][/tex]

Find the difference in simplest form.


Sagot :

To solve this problem, let's follow the steps to find the simplest form of the expression given:

Jesse is traveling up and down a stream in a kayak at an average rate of 5 miles/hour. The total distance of the round trip is 16 miles, which means each leg of the trip (upstream and downstream) is 8 miles. So, [tex]\( B = 8 \)[/tex].

The expression for the difference in time taken for upstream and downstream travel is given by:
[tex]\[ \frac{B}{5 - c} - \frac{B}{5 + c} \][/tex]

Substituting [tex]\( B = 8 \)[/tex], we get:
[tex]\[ \frac{8}{5 - c} - \frac{8}{5 + c} \][/tex]

To combine these fractions, we can find a common denominator. The common denominator for [tex]\( 5 - c \)[/tex] and [tex]\( 5 + c \)[/tex] is [tex]\( (5 - c)(5 + c) \)[/tex].

Thus, we write:
[tex]\[ \frac{8(5 + c)}{(5 - c)(5 + c)} - \frac{8(5 - c)}{(5 - c)(5 + c)} \][/tex]

Now, combine the numerators over the common denominator:
[tex]\[ \frac{8(5 + c) - 8(5 - c)}{(5 - c)(5 + c)} \][/tex]

Simplify the numerator:
[tex]\[ 8(5 + c) - 8(5 - c) = 40 + 8c - 40 + 8c = 16c \][/tex]

So the expression becomes:
[tex]\[ \frac{16c}{(5 - c)(5 + c)} \][/tex]

Notice that [tex]\( (5 - c)(5 + c) \)[/tex] is a difference of squares, which simplifies to:
[tex]\[ 25 - c^2 \][/tex]

Therefore, the simplified form of the expression is:
[tex]\[ \frac{16c}{25 - c^2} \][/tex]

Hence, the difference in time taken for upstream and downstream travel in simplest form is:
[tex]\[ \boxed{\frac{16c}{c^2 - 25}} \][/tex]