# Thread: Help with variable fraction exponent problem

1. ## Help with variable fraction exponent problem

50 + 50 + 1050 = 1000.89
1+i (1+i)2 (1+i)3

I know i should equal 4.9762%, but when I complete this equation I keep getting 3.962. Can someone please help me with this equation by showing the steps involved? Thank you so much!

2. ## Re: Help with variable fraction exponent problem

the solve feature of my calculator says $i = 0.04967338437 ...$

3. ## Re: Help with variable fraction exponent problem

Yeah, that's what my calculator gets also, but I'm not allowed to use a calculator with the solve feature on my exam. Thanks though!

4. ## Re: Help with variable fraction exponent problem

Originally Posted by RMath
Yeah, that's what my calculator gets also, but I'm not allowed to use a calculator with the solve feature on my exam. Thanks though!
You would not be given a question this difficult on a calculator-free exam. If you multiply by the LCD, you'll find that this is a cubic equation. All cubic equations have at least one real solution BUT finding these solutions, when there is not an obvious rational root (and in this case there won't be because of the decimal) is a LONG process.

If you really want to learn how to solve cubic equations exactly, I suggest you read this...