Answer:
k = -4
Step-by-step explanation:
The remainder theorem tells you that the remainder from division f(x)/(x -k) is f(k). You want the value of k such that ...
f(k) = -15
Looking on the given graph, you find that k must be -4. That is, ...
f(-4) = -15
k = -4
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The divisor with k=-4 is (x -(-4)) = (x +4). The second attachment shows the division of f(x) by (x+4). The remainder is shown on the bottom line.
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One method is to plot the points P(3,6) and Q(7,3) on the same xy grid. Plot a third point R at (3,3). See the diagram below.
A right triangle forms in which we can find the legs PR = 3 and RQ = 4. The hypotenuse is found through the pythagorean theorem.
a^2+b^2=c^2
3^2+4^2 = c^2
9+16 = c^2
c^2 = 25
c = sqrt(25)
c = 5
This is the length of PQ
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Or you can use the distance formula which is effectively using the pythagorean theorem just in a slightly different format (though it may not be obvious).
