3/7/2017
Prebell
WB p. 20 # 7
A rectangle has vertices 𝑊(−4, −6), 𝑋(−4, 8),
𝑌(4, 8), 𝑍(4, −6). Find its vertices after a
dilation with a scale factor of ½. Then, draw and
label the figure and its dilated image.
Scale Factor
Write a rule to describe the
transformation.
• Scale factor – ratio of corresponding side lengths of
the image to the original figure
• To find scale factor:
𝐾(−1, −2), 𝑈(−2, 2), 𝑉(2, 2), 𝑄(2, −1)
to
𝐾′(−2, −4), 𝑈′(−4, 4), 𝑉′(4, 4), 𝑄′(4, −2)
– Divide the image coordinates (primes) by the original
coordinates.
• Ex: Write a rule to describe the transformation.
𝑁(−4, 1), 𝑇(−5, 3), 𝐽(−4, 3), 𝐶 −1, 0
to
𝑁′(−1, 0.25), 𝑇′(−1.25, 0.75), 𝐽′(−1, 0.75), 𝐶′(−0.25, 0)
The blue figure is a dilation of the red
figure. Identify the type of dilation
and find the scale factor.
The blue figure is a dilation of the red
figure. Identify the type of dilation
and find the scale factor.
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3/7/2017
Identify the type of dilation and find
the scale factor.
Lissa is enlarging a digital photo that is 4 in.
high by 6 in. wide. The enlarged photo is
1
18 in. high. What is its width? What is
2
the scale factor?
You are reducing a digital photo that is 2 in.
high and 3 in. wide. If the reduced photo is
1
1 4 in. high, what is its width?
Describe each transformation shown in the
notations below. Are the preimage and
image congruent or similar?
1
5
1
5
(𝑥, 𝑦) → ( 𝑥, 𝑦)
(𝑥, 𝑦) → (𝑥, −𝑦)
(𝑥, 𝑦) → (2𝑥 + 4, 2𝑦 − 3)
1
1
(𝑥, 𝑦) → (3 𝑥, − 3 𝑦)
𝑥, 𝑦 → −𝑥 + 7, 𝑦 − 2
Describe a sequence of
transformations in which the blue
figure is the image of the red figure.
Describe a sequence of
transformations in which the blue
figure is the image of the red figure.
2