Questions on Algebra: Complex Numbers answered by real tutors!

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Question 147558: I'm not quite sure how to simplify the expression 4 over 2+5i (4/2+5i) and I'm not quite sure what i to the -35th power means.: I'm not quite sure how to simplify the expression 4 over 2+5i (4/2+5i) and I'm not quite sure what i to the -35th power means.
Answer by jim_thompson5910(9368) About Me  (Show Source):
You can put this solution on YOUR website!
(4)/(2+5i) Start with the given expression.


((4)/(2+5i))((2-5i)/(2-5i)) Multiply both numerator and denominator by the complex conjugate of 2+5i


((4)(2-5i))/((2+5i)(2-5i)) Combine the fractions


((4)(2-5i))/(29) Foil the denominator to get (2+5i)(2-5i)=4-10i+10i-25i^2=4-25(-1)=29


(8-20i)/(29) Distribute


So (4)/(2+5i)=(8-20i)/(29)


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i^(-35) Start with the given expression.


1/i^(35) Flip the fraction to make the exponent positive.

Now let's find evaluate i^(35):

First take the exponent 35 and divide by 4.
When it leaves a remainder of 0, the answer is 1.
When it leaves a remainder of 1, the answer is sqrt(-1)=i.
When it leaves a remainder of 2, the answer is -1.
When it leaves a remainder of 3, the answer is -sqrt(-1)=-i.


Since 35/4 leaves a remainder of 3, this means the answer is -i.


So i^35=-i


So this means that


1/i^(35)=1/(-i)




1/(-i) Start with the given expression.



(1/(-i))(i/i) Multiply both numerator and denominator by "i"


(1*i)/((-i)(i)) Combine the fractions.


(1*i)/(-i^2) Multiply i and i to get i^2


(1*i)/(-(-1)) Replace i^2 with -1. Remember i^2=-1


(i)/(1) Multiply


i Simplify


So i^(-35)=i
Question 147558: I'm not quite sure how to simplify the expression 4 over 2+5i (4/2+5i) and I'm not quite sure what i to the -35th power means.: I'm not quite sure how to simplify the expression 4 over 2+5i (4/2+5i) and I'm not quite sure what i to the -35th power means.
Answer by stanbon(18991) About Me  (Show Source):
You can put this solution on YOUR website!
I'm not quite sure how to simplify the expression 4 over 2+5i (4/2+5i) and I'm not quite sure what i to the -35th power means.
----------------------------
4/(2+5i)
----
Multiply numerator and denominator by (2-5i) to get:
[4(2-5i)]/[4+25]
= (8-20i)/29
-----------------
i^(-35)
Applying the -1 exponent you get:
(i^3)^35
Applying the 35 exponent you get:
= i^105
= i^(104+1)
= i^(104) * i^1
= 1 * i^1
= i
=============
Cheers,
Stan H.
Question 147558: I'm not quite sure how to simplify the expression 4 over 2+5i (4/2+5i) and I'm not quite sure what i to the -35th power means.: I'm not quite sure how to simplify the expression 4 over 2+5i (4/2+5i) and I'm not quite sure what i to the -35th power means.
Answer by Nate(3495) About Me  (Show Source):
You can put this solution on YOUR website!
i^(-35)
1/i^35
1/( i * i^34 ) ~ you want an even power
1/( i * (i^2)^17 ) ~ now, you want an exponent of 2
1/( i * (-1)^17 ) ~ i^2 = -1
-1 / i ~ (-1)^17 = -1
..
4 / (2 + 5i)
4(2 - 5i) / (2 + 5i)(2 - 5i) ~ multiply the num. and dem. by the conjugate