Thread: Solving an exponential equation with two unknowns

solve the following system:

2^(x+3y) = 128

Originally Posted by math123456

solve the following system:

2^(x+3y) = 128

Start by solving x + 3y = 7.

Not 100% sure here, but.

To solve for y.

Rewrite 128 as 2 to the something power, which is:

2 to the 7th power.

Set x+3y equal to 7.

x+3y = 7
3y = -x + 7
y = -(x-7)/3

Same for x, except solve x+3y = 7 for x.
x = -3y + 7

I believe this is how it's done.

Originally Posted by IAmLegendToo

Not 100% sure here, but.

To solve for y.

Rewrite 128 as 2 to the something power, which is:

2 to the 7th power.

Set x+3y equal to 7.

x+3y = 7
3y = -x + 7
y = -(x-7)/3

Same for x, except solve x+3y = 7 for x.
x = -3y + 7

I believe this is how it's done.

Because there are 2 variables in the one equation there will be infinite solutions that lie on the line

You said, in your first post, "Solve the following system" (my emphasis). You did not give a system. What does the problem really say?