# Formulae: Unit 19

• Created by: annanolan
• Created on: 03-01-17 13:11
What does ∝ mean?
directly proportional to
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what does y equal if it directly proportional to x?
y=kx
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What is k?
A constant
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what does y equal if it directly proportional to x²?
y=kx²
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what does y equal if it directly proportional to √x?
y=k√x
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what does y equal if it inversely proportional to x?
y=k/x
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What is y inversely proportional to?
y∝1/x
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What are exponential functions?
Expressions of the form aˣ, where a is a positive number
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What is the graph of exponential growth?
.
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What is the graph of exponential decay?
.
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What does the gradient of the line on a distance-time graph show?
The speed
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What is the straight line that connects two points on a curve called?
a chord
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What does the gradient of the chord show?
The average rate of change which can be used to find the average speed on a distance-time graph
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What does the area under a velocity-time graph show?
The displacement or distance from the starting point
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How do you estimate the area under a part of a curved graph?
draw a chord between the two points you are interested in and straight lines down to the horizontal axis
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How is the graph of y=f(x) transformed into y=f(x)+a
translation by vector ( 0 over a)
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How is the graph of y=f(x) transformed into y=f(x+a)
translation by vector (-a over 0)
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Describe the transformation from y=f(x) onto y=f(-x)
a reflection in the y-axis
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Describe the transformation from y=f(x) onto y=-f(x)
a reflection in the x-axis
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How is the graph of y=f(x) transformed into the graph of y=af(x)
by a stretch of scale factor a parallel to the y-axis
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How is the graph of y=f(x) transformed into the graph of y=f(ax)
by a stretch of scale factor 1/a parallel to the x-axis
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## Other cards in this set

### Card 2

#### Front

what does y equal if it directly proportional to x?

y=kx

What is k?

### Card 4

#### Front

what does y equal if it directly proportional to x²?

### Card 5

#### Front

what does y equal if it directly proportional to √x?