Question

I need Help..

Determine which point lies on the graph of the equation 9x^2+x-1

A. (1,9)
B. (1,7)
C. (2,9)
D. (3,8)
E. (2,7)

Id like an explanation/shown on how you got the answer. Please and thank you

Answer 1

(1, 9) lies on the graph

Explanation:

I found this result by graphing the curve and the points.

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Writing the equation in "Horner form" makes it relatively easy to evaluate. There are only 3 values of x to try: 1, 2, 3.

y = (9x +1)x -1

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x = 1: y = (9·1 +1)1 -1 = 10 -1 = 9 . . . . . (1, 9) matches choice A (not B)

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x = 2: y = (9·2 +1)2 -1 = 38 -1 = 37 . . . . (2, 37) matches no choice

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We can see that for larger values of x, y is increasing very rapidly, so the only reasonable choice is (1, 9).