indices/ logarithms..help!

[Mulan]

how do you solve 5^2x - 5^x+1 = -4   ??

[Mao]

Let A = 5^x

A^2 - 5A  + 4 = 0

use quadratic formula.

[Mulan]

Let A = 5^x

A^2 - 5A  + 5 = 0

use quadratic formula.

thats what I did but i got the wrong answer D:
the answers x = 0.86, 0 but i got x = 1,4
i just factorised it to find x, not the quadratic formula. is that wrong?

[Mao]

You are almost there, , thus solve and

[Mulan]

You are almost there, , thus solve and

omg yea! woopsies.
i forgot that I made 5^x=Y
thanks so much

[Mulan]

can you help me with another question? xD
solve 5(3^x) - 40 (3^-x)=17 for x

[kamil9876]

multiply both sides by , notice that you get a quadratic similair to the one before.

[Mulan]

multiply both sides by , notice that you get a quadratic similair to the one before.

y do you multiply both sides by 3^x?

[m@tty]

So that

you get a quadratic similair to the one before.

It is much easier to solve.





. where (which holds for all real numbers.)

Then solve as a quadratic in as before.

[Mulan]

So that

you get a quadratic similair to the one before.

It is much easier to solve.





. where (which holds for all real numbers.)

Then solve as a quadratic in as before.

ohhhh thanks you guys really helped a lot