justmathshelp
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unsure how to do 2D
I understand how to answer these questions but i get stuck at the first part when making y = to something
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justmathshelp
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Muttley79
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(Original post by justmathshelp)
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Use the hint and substitute y = 3^x
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Maivnek
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Have you considered it a hidden quadratic?
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justmathshelp
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(Original post by Muttley79)
Use the hint and substitute y = 3^x
with the hint - 3(3^x) i don't understand this? how does this equal 3^x
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justmathshelp
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(Original post by Maivnek)
Have you considered it a hidden quadratic?
thats how you solve these questions and i know that my problem is above ^
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ollseph
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32x + 3x+1 – 10 = 0

32x + 3(3x) – 10 = 0

Make y = 3x

y2 + 3y – 10 = 0

(y+5)(y-2) = 0

y = -5, y = 2


3x = -5 , no solutions

3x = 2 , log 2/log 3
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Maivnek
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Just follow these steps.

Use the log laws to isolate 3^x.
Substitute 3^x for, say, t.
Solve for t.
Plug in 3^x.
Solve for x.

Edit: nevermind ollseph has got full solution
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justmathshelp
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(Original post by Maivnek)
Just follow these steps.

Use the log laws to isolate 3^x.
Substitute 3^x for, say, t.
Solve for t.
Plug in 3^x.
Solve for x.

Edit: nevermind ollseph has got full solution

i said before i know the steps my problem is making y = to something and im not asking for the answer just unsure how y = 3^x
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Maivnek
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3^2x = (3^x)^2 according to exponent laws and hint.
3^x+1 = 3*3^x
Now you can substitute
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anosmianAcrimony
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Use a chainsaw.
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justmathshelp
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(Original post by Maivnek)
3^2x = (3^x)^2 according to exponent laws and hint.
3^x+1 = 3*3^x
Now you can substitute
with 3*3^x

the first 3 has a power to 1 yeah? so thats where the 1 comes from in 3^x+1
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Maivnek
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y is just a placeholder for 3^x and is just an unassigned letter. You're substituting 3^x because you can't deal with the equation in it's complete form, but you know how to deal with a quadratic. And saying 3^x = y creates a quadratic.
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Maivnek
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(Original post by justmathshelp)
with 3*3^x

the first 3 has a power to 1 yeah? so thats where the 1 comes from in 3^x+1
Yes. and an exponent law says: a^(m+n) = a^m * a^n
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Muttley79
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(Original post by ollseph)
....
Please edit your post - we do NOT give full solutions in maths. Please read the rules ...
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Muttley79
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(Original post by justmathshelp)
i said before i know the steps my problem is making y = to something and im not asking for the answer just unsure how y = 3^x
We are trying to 'reveal' the underlying quadratic.

We could use any letter but we just tend to use y.
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justmathshelp
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(Original post by Muttley79)
Please edit your post - we do NOT give full solutions in maths. Please read the rules ...
thanks
it was pretty pointless anyway i know how to do these questions i was just unsure what to make y =
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justmathshelp
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#18
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(Original post by Maivnek)
Yes. and an exponent law says: a^(m+n) = a^m * a^n
yeah thanks x
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