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Here we will learn about exponential graphs, including recognising, sketching, plotting and interpreting exponential graphs.
There are also exponential graphs worksheets based on Edexcel, AQA and OCR exam questions, along with further guidance on where to go next if youβre still stuck.
An exponential graph is a representation of an exponential function of the form
Where
The
The
The curve gets very close to the horizontal asymptote but does not touch it. This is because
The graph of an exponential function can represent either exponential growth or exponential decay:
E.g.
E.g.
There are more complex exponential functions of the form:
The graphs look similar to the ones above, they have an exponent
E.g.
Exponential graphs can represent two types of problems, growth and decay. They involve real-life situations.
Growth problems are when the amount increases over time. An example is how a population increases over time.
Decay problems are when the amount decreases over time. An example is the amount of radiation from a radioactive substance over time.
In order to recognise an exponential graph:
Get your free exponential graph worksheet of 20+ types of graphs questions and answers. Includes reasoning and applied questions.
DOWNLOAD FREEGet your free exponential graph worksheet of 20+ types of graphs questions and answers. Includes reasoning and applied questions.
DOWNLOAD FREEExponential graph is part of our series of lessons to support revision on types of graphs. You may find it helpful to start with the main types of graphs lesson for a summary of what to expect, or use the step by step guides below for further detail on individual topics. Other lessons in this series include:
Which is the correct equation for the graph?
y=x^2+3 is a quadratic function; its graph would be a parabola.
y=3x+1 is a linear function; its graph would be a straight line.
y=\frac{3}{x} is a reciprocal function; its graph would be a hyperbola.
2Identify the exponential function
y=3^x is an exponential function.
It has
So the graph would be a growth curve.
3Identify your final answer
The correct equation for the graph is y=3^x
Which is the correct equation for the graph?
Identify linear or quadratic or any other functions
y=1-3x is a linear function; its graph would be a straight line.
y=x^2-3 is a quadratic function; its graph would be a parabola.
y=x^3 is a cubic function.
Identify the exponential function
y=(\frac{1}{3})^x is an exponential function.
It has
So the graph would be a decay curve.
Identify your final answer
The correct equation for the graph is y=(\frac{1}{3})^x
In order to plot an exponential graph:
Draw the curve of the equation for -1\leq{x}\leq3
y=2^xComplete the table of values
Plot the coordinates
Draw an
Draw a smooth curve through the points
Draw the curve of the equation for -2\leq{x}\leq2
y=(\frac{1}{2})^xComplete the table of values
Plot the coordinates
Draw an
Draw a smooth curve through the points
In order to find the equation of an exponential graph:
The sketch shows a curve with equation y = ab^x where
Find the equation of the curve.
Substitute the pairs of values into the given equation
The given equation is:
Substituting
Substituting
Solve the two simultaneous equations
Since b^{0} = 1, this becomes a = 2
Now we look at the second equation:
But we know that
This can be solved to find the base
Write down the equation of the exponential function
The original equation was:
We found that
The sketch shows a curve with equation y = ab^x where
Find the equation of the curve.
Substitute the pairs of values into the given equation
The given equation is:
Substituting
Substituting
Solve the two simultaneous equations
Since anything to the power
Now we look at the second equation:
We can solve these two equations by dividing one by the other:
This becomes:
This can be solved to find the base
We can substitute b = 2 into one of the equations to find a:
Write down the equation of the exponential function
The original equation was:
We found that
Do NOT join up the plotted points with straight lines like this:
The points should be joined by a single, smooth curve.
If there is a point that does not join up with the other points when a smooth curve is drawn, this point is incorrect.
1. Identify the correct equation for the graph:
The curve is a growth curve; its equation will be an exponential function.
y=6^x is an exponential function.
y=6x+1 is a linear function; its graph would be a straight line.
y=x^2+1 is a quadratic function; its graph would be a parabola.
y=\frac{6}{x} is a reciprocal function; its graph would be a hyperbola.
2. Identify the correct equation for the graph:
The curve is a decay curve; its equation will be an exponential function.
y=0.1^x is an exponential function.
y=1-10x is a linear function; its graph would be a straight line.
y=x^2+1 is a quadratic function; its graph would be a parabola.
y=x^3+1 is a cubic function.
Identify the correct equation for the graph:
y=10^x
A correct table of values would be:
0 1 2
1 10 100
These x values and y values give coordinates such as (0, 1), (1, 10) and (2,100).
The coordinates are plotted on the grid.
A smooth curve should be drawn through the points.
4. Identify the correct graph for the equation:
y=(\frac{1}{5})^x
A correct table of values would be:
-2 -1 0 1
25 5 1 0.2
These x values and y values give coordinates such as (-2, 25), (-1, 5) and so on.
The coordinates are plotted on the grid.
A smooth curve should be drawn through the points.
5. Find the equation of the curve in the form
y=ab^x
where a and b are constants and b > 0.
Substituting the coordinates into the given equation gives
4=ab^0=a
Now we need to find the base b
32 = ab^3
32= 4\times b^3
8 = b^3
b = \sqrt[3]{8}
b = 2
So the equation is:
y=4\times 2^x
6. Find the equation of the curve in the form
y=ab^x
where a and b are constants and b > 0.
Substituting the coordinates into the given equation gives
21=ab^1=ab
189=ab^3
Dividing the two equations
\frac{189}{21} = \frac{ab^3}{ab}
9 = b^2
b = \sqrt{9}
b = 3
We can substitute b = 3 into one of the equations to find a.
21 = ab
21 = a\times 7
a = 7
So the equation is:
y=7\times 3^x
1.Β Match the correct graph to the equation.
y=8^{x}
(1 Mark)
Graph C
(1)
2.Β (a) Complete the table of values for y=4^x
\begin{aligned} &x \quad \quad -1 \quad \quad 0 \quad \quad 1 \quad \quad 2 \\ &y \end{aligned}
(b) On the grid, draw the graph of y=4^{x} for -1\leq{x}\leq2
(4 Marks)
(a)
Correct values are: 0.25, 1, 4 and 16
For 1 correct y -value
(1)
For all correct y -values
(1)
(b)
for plotting the 4 points correctly
(1)
for the smooth curve
(1)
3. Here is a sketch of part of the graph y=pq^{x} where q\gt0
The points (0,3), (2,k) and (4,1875) are all on the graph y=pq^{x}
Find the value of k.
(4 Marks)
3=pq^0 = p .
for p = 3
(1)
1875=pq^4 = 3\times q^4 .
(1)
q=\sqrt[4]{625}=5 .
for q=5
(1)
k=3\times 5^2=75 .
for the correct value of k
(1)
You have now learned how to:
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