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logs help

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

Original post by justmathshelp

Use the hint and substitute y = 3^x

Reply 3

Maivnek

Have you considered it a hidden quadratic?

Reply 4

justmathshelp

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

Reply 5

justmathshelp

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 ^

Reply 6

ollseph

3^2x + 3^x+1 – 10 = 0

3^2x+ 3(3^x) – 10 = 0

Make y = 3^x

y²+ 3y – 10 = 0

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

y = -5, y = 2

3^x= -5 , no solutions

3^x = 2 , log 2/log 3

Reply 7

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

(edited 6 years ago)

Reply 8

justmathshelp

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

Reply 9

Maivnek

3^2x = (3^x)^2 according to exponent laws and hint.
3^x+1 = 3*3^x
Now you can substitute

Use a chainsaw.

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

Reply 12

Maivnek

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.