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Which statement is correct with respect to f(x) = -3|x − 1| + 12?

A.
The V-shaped graph opens upward, and its vertex lies at (-3, 1).

B.
The V-shaped graph opens downward, and its vertex lies at (-1, 3).

C.
The V-shaped graph opens upward, and its vertex lies at (1, -12).

D.
The V-shaped graph opens downward, and its vertex lies at (1, 12).

User Knt
by
7.3k points

2 Answers

5 votes

Let's start from the parent function
y = |x| and see which transformation we have applied. The parent function's graph is open upards, and its vertes lies at
(0,0)

The first transformation is
|x| \to |x-1|. This is a tranformation of the form
f(x)\to f(x+k). This kind of transformation shift the graph horizontally, k units to the left if k is positive, k units to the right if k is negative. In this case
k = -1, so the function is shifted one unit to the right. The new vertex lies at
(1,0)

The second transformation is
|x-1| \to -3|x-1|. This is a tranformation of the form
f(x)\to kf(x). This kind of transformation stretch the graph vertically, compressing it if k is between 0 and 1, expanding it if k is greater than 1. Moreover, if k is negative, the function is reflected along the x axis. In this case
k = -3, so the function is reflected and stretched. This means that now the graph opens downwards, the vertex still lies at
(1,0).

Finally, we have
-3|x-1| \to -3|x-1|+12. This is a tranformation of the form
f(x)\to f(x)+k. This kind of transformation translates the graph vertically, k units up if k is positive, k units down if k is negative. In this case,
k = 12, so the graph is shifted 12 units up. The graph still opens downwards, while the new vertex lies at
(1,12)

User ITSrAVIE
by
7.1k points
7 votes

The answer should be D if not it is C

User Tilde
by
8.0k points