# alg 2.

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solve. we can use a calculator on this part...
2e^-x+4=21. how do i do this problem.

i know that you subtract 4, but what do you do after that?

• alg 2. -

2e^-x+4=21
2 e^-x = 17
e^-x = 17/2
1/e^x = 17/2
so
e^x = 2/17
take natural log of both sides
x = ln (2/17)

• alg 2. -

can you please show me how you got e^x=2/17. thanks

• alg 2. -

in general
a^-b = 1/a^b

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