What are the zeroes of f(x) = x^2 - 2x - 3?
x = -3, 1
x = -3, -1
x = 3, 1
x = 3, -1
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OpenStudy (muzzack):
try to replace x with each number
OpenStudy (anonymous):
f(x)=x^x-xx-x ?
OpenStudy (skullpatrol):
What is that^ @Alexandra675 ?
OpenStudy (anonymous):
lol he said to replace x with each number sooo...
OpenStudy (skullpatrol):
there is no x^x
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OpenStudy (anonymous):
x^2
OpenStudy (skullpatrol):
look at the answers:
x = -3, 1
x = -3, -1
x = 3, 1
x = 3, -1
they don't make sense do they?
OpenStudy (anonymous):
Kinda the the 3 is from the problem I don't know where they got the 1 from...
OpenStudy (skullpatrol):
A point has coordinates (x, y)
OpenStudy (anonymous):
yea
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OpenStudy (skullpatrol):
What does "x = -3, 1 " mean?
OpenStudy (anonymous):
That there are two points and those are both the x coordinats?
OpenStudy (muzzack):
so you do \(\huge\ -3^2 - 2(-3) - 3\) and \(\huge\ -1^2 - 2(-1) - 3\)
OpenStudy (skullpatrol):
Nope. It should be written as "x = -3, y = 1 "
OpenStudy (anonymous):
oh ok so where does the 1 come from?
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OpenStudy (muzzack):
oh yes your totally right @skullpatrol
OpenStudy (muzzack):
sorry
OpenStudy (anonymous):
XD
OpenStudy (skullpatrol):
The 1 is what y equals.
OpenStudy (muzzack):
\(\huge\ -3^2 - 2(-3) - 3 =1\)
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OpenStudy (anonymous):
oh ok so its A then?
OpenStudy (skullpatrol):
Sorry, that is wrong :(
geerky42 (geerky42):
huh what are you talking about? @skullpatrol
Zeros of f(x) is x = -3, 1 means f(x) = 0 at x= -3 or x=1
OpenStudy (skullpatrol):
The equation has 2 solutions for x
geerky42 (geerky42):
that "1" part is not y.
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OpenStudy (skullpatrol):
Can we start again @Alexandra675 ?
OpenStudy (anonymous):
Like do the problem over? Sure
OpenStudy (skullpatrol):
Yes, I confused it with your first question, sorry about that.
OpenStudy (anonymous):
What are the zeroes of f(x) = x^2 - 2x - 3?
x = -3, 1
x = -3, -1
x = 3, 1
x = 3, -1
OpenStudy (anonymous):
lol y did I do tht XD
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OpenStudy (skullpatrol):
start by factoring x^2 - 2x - 3
OpenStudy (anonymous):
\[(x-3)(x+1)\]
OpenStudy (skullpatrol):
Correct! now set it equal to 0
OpenStudy (anonymous):
x=3,-1
OpenStudy (skullpatrol):
and tell me for what values of x will it be true
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OpenStudy (anonymous):
???
OpenStudy (skullpatrol):
Yes for x=3 or x=-1, x^2 - 2x - 3 = 0
OpenStudy (skullpatrol):
those are the "zeros"
OpenStudy (anonymous):
Hold on let me work this out
OpenStudy (skullpatrol):
please do :)
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OpenStudy (anonymous):
The first one works
OpenStudy (anonymous):
I think...
OpenStudy (luigi0210):
If you factored them correctly, then they should be right, just watch out for the extraneous solutions.
OpenStudy (anonymous):
The second one equals -2 tho
OpenStudy (anonymous):
No what is it still correct?
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OpenStudy (anonymous):
...
OpenStudy (anonymous):
@skullpatrol
OpenStudy (luigi0210):
If you factor \(x^2-2x-3\) you get \((x-3)(x+1)\) right?
Now solve them \(0=(x-3), 0=(x+1)\)
You will get \(x=3, -1\)
If you plug them in:
\(0=(3)^2-2(3)-3\) you get \(0=9-6-3\) which is just \(0=0\) so that works.
Plug in -1
\(0=(-1)^2-2(-1)-3\) you get \(0=1+2-3\) which is also \(0=0\)
So those points work, as @skullpatrol said
OpenStudy (anonymous):
Oh ok I guess I did my calculations wrong for -1 thank you!