Absolute Value

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Absolute Value

Definition

𝑥, 𝑖𝑓 𝑥 𝑖𝑠 𝑝𝑜𝑠𝑖𝑡𝑖𝑣𝑒 lxl = 0, 𝑖𝑓 𝑥 = 0

−𝑥, 𝑖𝑓 𝑥 𝑖𝑠 𝑛𝑒𝑔𝑎𝑡𝑖𝑣𝑒

If x = 3, then the absolute value of x = 3.

If x = -3, then the absolute value of x = -(-3), or x = 3.

Parent Function Graph y = lxl

2

1,5

1

0,5

3,5

3

2,5

0

-4 -2 0 2 4 x

Vertex – highest of lowest point on the graph of an absolute value function. For this graph the vertex is (0,0).

Transformations

A transformation changes a graph’s size , shape , position , or orientation .

A translation is a transformation that shifts a graph horizontally and/or vertically. It does NOT change its size, shape, or orientation – only the position .

Translation of Absolute Value Graph

The graph of y = lx-hl + k is the graph of y = lxl translated h units horizontally and k units vertically. The vertex of is (h,k).

Y=lxl

(0,0) h

(h,k) k y = lx-hl + k

Graph y = lx+5l – 1. Compare with the graph of y = lxl.

Step 1 : Identify and plot the vertex.

Step 2 : Plot another point on the graph. Use symmetry to plot a third point.

Step 3 : Connect the points with a V-shaped graph.

Step 4 : Compare the graphs. Use the word translated in your comparison. How did domain and range change?

Stretches and Shrinks

The graph y = alxl is a vertical stretch or shrink of the graph y = lxl when a ≠ 1.

For lal > 1

The graph is vertically stretched, or elongated.

For lal<1

The graph is vertically shrunk, or compressed.

The graph is narrower.

The graph is wider.

Choose one and graph it with your table!

a = 3, 5, ½ , or ¼

Reflections (FLIPS)

When a = -1, then y = alxl is a reflection in the x-axis of y = lxl. When a is negative number besides -1, it is a vertical stretch or shrink with a reflection across the x-axis.

Y = lxl

Y = -lxl

Multiple Transformations

A graph may be related to a parent graph by even more than 2 transformations. y = a lx-hl +k can involve a stretch or shrink, a reflection, and a translation of y = lxl.

Example

y = -3 lx-1l +2 Stop and think about what each part does.

y = a lx-hl +k h,k translates the graph. The new vertex would be (1,2).

lal tells you whether you shrink or stretch. Since 3 > 1 then the graph is narrower – vertically stretched.

Negative a means you flip so since here we have -3 the graph will be flipped.

Put it into practice

Do the following problems with your shoulder partner.

Pg. 127: 3-7

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