- #1

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**Question**

Expand (e^x + e^-x)^2

I've got the answer but i'm just stumped at how to reach it, I dunno where the 2 comes from:

**Answer**

e^2x + 2 + e^-2x

Thanks (and sorry again)

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- Thread starter Crosshash
- Start date

- #1

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Expand (e^x + e^-x)^2

I've got the answer but i'm just stumped at how to reach it, I dunno where the 2 comes from:

e^2x + 2 + e^-2x

Thanks (and sorry again)

- #2

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- #3

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Sorry, the +2. I can reach the e^2x + e^-2x but I can't reach the "+2" which means the method I'm using is incorrect.

I haven't touched this stuff in a while so I'm just trying to re-remember it.

- #4

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Remember, (a+b)^2 = a^2 + 2ab + b^2 (use foil), NOT a^2 + b^2

- #5

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Remember, (a+b)^2 = a^2 + 2ab + b^2 (use foil), NOT a^2 + b^2

Yeah, i tried using foil.

Foil if I'm not mistaken would grant me.

(e^x + e^-x) (e^x + e^-x)

(e^x * e^x) + (e^x * e^-x) + (e^-x * e^x) + (e^-x * e^-x)

(e^2x) + (1) + (1) + (e^-2x)

(e^2x) + (2) + (e^-2x)

Is that right?

- #6

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Yep, looks good.

- #7

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aha, thanks for the help. Just got a bit confused with the powers for a moment it seems.

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