Math Is Fun Forum

nycguitarguy

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 566

Find x-intercepts of Two Graphs

Suppose that the x-intercepts of the graph y = f(x) are -8 and 1.

A. What are the x-intercepts of the graph of y = 2•f(x)?

B. What are the x-intercepts of the graph of y = f(-x)?

Last edited by nycguitarguy (2024-04-15 10:45:39)

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The Rapture is the central event in biblical prophecy. The greatest truth about the Rapture is not its timing but it's reality. The Rapture will be the great disappearance.

Dr. David Jeremiah

nycguitarguy

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 566

Re: Find x-intercepts of Two Graphs

For A.

Multiply each x-coordinate of y = f(x) by 1/a.

Let a = 2

1/2 • (-8) = -4

1/2 • (1) = 1/2

You say?

For B.

Let y = f(-x)

So, -(-8) = 8

And

-(1) = -1

You say?

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The Rapture is the central event in biblical prophecy. The greatest truth about the Rapture is not its timing but it's reality. The Rapture will be the great disappearance.

Dr. David Jeremiah

Bob

Administrator

Registered: 2010-06-20

Posts: 10,208

Re: Find x-intercepts of Two Graphs

I think that's ok. Is part of the question missing?

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

nycguitarguy

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 566

Re: Find x-intercepts of Two Graphs

I think that's ok. Is part of the question missing?

Bob

Hi Bob.

Here is the entire question:

Suppose that the x-intercepts of the graph y = f(x) are -8 and 1.

A. What are the x-intercepts of the graph of y = 2•f(x)?

B. What are the x-intercepts of the graph of y = f(-x)?

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The Rapture is the central event in biblical prophecy. The greatest truth about the Rapture is not its timing but it's reality. The Rapture will be the great disappearance.

Dr. David Jeremiah

Bob

Administrator

Registered: 2010-06-20

Posts: 10,208

Re: Find x-intercepts of Two Graphs

Oh I see what happened. I read post 2 not noticing post 1.

Part B correct not A. It's to do with where the 2 is . Inside the bracket, ok. Outside it doubles the y coordinate and does nothing to the x.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

nycguitarguy

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 566

Re: Find x-intercepts of Two Graphs

Oh I see what happened. I read post 2 not noticing post 1.

Part B correct not A. It's to do with where the 2 is . Inside the bracket, ok. Outside it doubles the y coordinate and does nothing to the x.

Bob

Let me try again.

Part A

We are told the x-intercepts for the original function y = f(x) are -8 and 1 which can be written as (-8, 0) and (1, 0).

We are also told that  y = 2f(x). Since 2 > 0, I multiply each y-coordinate by 2.

So, (-8, 2(0)) and (1, 2(0)) = (-8, 0) and (1, 0).

The x-intercepts of y = 2f(x) are the same as those for the original function y = f(x).

Part B

Set the argument for y = f(-x) to each given x-intercept for the original function and solve for x.

-x = -8

x = -8/-1

x = 8

-x = 1

x = 1/-1

x = -1

The x-intercepts for the graph of y = f(-x) are (8,0) and (-1,0).

You say?

Last edited by nycguitarguy (2024-04-17 09:08:17)

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The Rapture is the central event in biblical prophecy. The greatest truth about the Rapture is not its timing but it's reality. The Rapture will be the great disappearance.

Dr. David Jeremiah

Bob

Administrator

Registered: 2010-06-20

Posts: 10,208

Re: Find x-intercepts of Two Graphs

Both now correct, well done.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

nycguitarguy

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 566

Re: Find x-intercepts of Two Graphs

Both now correct, well done.

Bob

Very cool.

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The Rapture is the central event in biblical prophecy. The greatest truth about the Rapture is not its timing but it's reality. The Rapture will be the great disappearance.

Dr. David Jeremiah