SOLUTION: what is the absolute value function of y=-|x|+1 how do i graph it?

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Question 216470: what is the absolute value function of y=-|x|+1 how do i graph it?

Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
There are a couple of ways we can graph this.

Solution 1: If you know what the graph of y+=+abs%28x%29 then you can figure out y+=+-abs%28x%29+%2B+1:
  • The "-" in front of the absolute value causes the graph to be reflected in the x-axis.
  • The "+1" causes the graph to be raised up 1 unit.
  • Putting these together, the graph of y+=+-abs%28x%29+%2B+1 is the graph of y+=+abs%28x%29 reflected in the x-axis and then raised up 1.

Solution 2: Use what you know about absolute value to rewrite y+=+-abs%28x%29+%2B+1 as a piecewise function. (This will make more sense when you see it.) What do we know about absolute value? We know that
  • The absolute value of any positive number is itself.
  • The absolute value of zero is itself
  • The absolute value of any negative number is the negative of its negative self (IOW, the "positive version" of itself)

To put this in algebraic terms:
If x+%3E=+0 then abs%28x%29+=+x
If x+%3C+0 then abs%28x%29+=+-x
Now we can use these to rewrite y+=+-abs%28x%29+%2B+1 in two ways, one for x+%3E=+0 and another for x+%3C+0:
If x+%3E=+0 then y+=+-x+%2B+1
If x+%3C+0 then y+=+-%28-x%29+%2B+1+=+x+%2B+1
And we can use these to graph y+=+-abs%28x%29+%2B+1. On a graph x+%3E=+0 is on the y-axis and to the right of the y-axis and x+%3C+0 is to the left of the y-axis. So we graph y+=+-x+%2B+1, which is a simple line (slope = -1, y-intercept = 1) just from the y-axis and to the right. And then, on the same graph, graph y+=+x+%2B+1, which is also a simple line (slope = 1, y-intercept of 1), just to the left of the y-axis.

Either way we should end up with a graph that looks somewhat like an upside down "v" with the point of the "v" at (0,1).