Are these correct

[chrystal21]

Hello! I am new, and would like to know if anybody can PLEASE check and see if I have the right answers, and if wrong can somebody please help me find the correct one? Thank you!!

1. Simplify i^42
a) 1
b) i
c) -1
d) -i
*I chose choice a

2) 4-2i/3+5i
a) -12i/17
b) 1/17 - 13/17i
c) 8/34 - 22/34i
d) 22/17 - 26/17 i
*choice a

3) Subtract: (9-6i) - (-7i-5)
a) 4-13i
b) 4+i
c) 14-13i
d) 14+i
*I chose choice d, is that correct?

4) express in terms of i and simplify: Square root of -243
a) 9i square root 3
b) 12 square root 2i
c) 9 square root 2i
d) -12 square root 2i
* Choice A

5) Find one of the solutions of x= square root of 2x-6 +3
a) -6
b) 8
c) -3
d) 5

 

[tkhunny]

Since you started badly, I didn't look at the rest.

i^42 = i^40 * i^2 = (i^4)^10 * i^2 = 1^10 * i^2 = 1 * i^2 = i^2 = -1

Pull out the multiples of 4. No guessing!

 

[jolly]

I'd like to see some of chrystal's work, too.

 

[chrystal21]

I'm having alot of difficulty trying to solve these types of problems. I've been looking all over websites for a tutorial help possibly and even looking through my text for step by step help but for some reason I'm not getting the hang of it. Can somebody maybe show me the 1st couple of steps in the problems?

 

[jolly]

Then where did the "answers" that you typed in come from?

 

[chrystal21]

Oh those answers I was plugging numbers into my calculator. I have difficulty trying to show work and coming up with an answer like that. Are those answers at least correct?

 

[stapel]

I've been looking all over websites for a tutorial help...

So you're needing lessons, so you can learn how to approach these exercises...? Please consider the following:

. . . . .Ask Dr. Math FAQ: Imaginary Numbers

. . . . .WTAMU: Complex Numbers Tutorial

. . . . .An introduction to complex numbers

. . . . .Complex Numbers

. . . . .Complex Numbers: Introduction

. . . . .Ask Dr. Math: Imaginary/Complex Numbers Archive

Once you have learned the basic techniques, please attempt the exercises. If you get stuck, please reply showing your work and reasoning.

Thank you.

Eliz.

 

[Gene]

I can't picture what you did to that poor calculator to get that for #1.
#2 you might have entered 4-2i/3+5i (that gives something close to what you picked) when you should have entered (4-2i)/(3+5i)
-----------------
Gene

 

[christina18]

I have a calculator and I also bought a math program for my computer that also helps me out. That is why I am asking for help from people that might know more then a program does. Why can't somebody just tell me if I am correct or incorrect and tell me or at least show me the first couple of steps in getting the answer? I read other boards that people posted and it seems as if there problem got helped 1,2,3...and I did visit those websites given, but all I ask is for somebody to PLEASE help me on the problems that I wrote :?

 

[jolly]

I have a calculator and I also bought a math program for my computer that also helps me out. That is why I am asking for help from people that might know more then a program does. Why can't somebody just tell me if I am correct or incorrect and tell me or at least show me the first couple of steps in getting the answer? I read other boards that people posted and it seems as if there problem got helped 1,2,3...and I did visit those websites given, but all I ask is for somebody to PLEASE help me on the problems that I wrote :?

But you didn't post these problems. Why are you getting involved?

 

[chrystal21]

me and Christina are in the same math class and both need help. She was logged in earlier under her name and I forgot to switch to my name since we are trying to do hw together sorry

 

[jolly]

me and Christina are in the same math class and both need help. She was logged in earlier under her name and I forgot to switch to my name since we are trying to do hw together sorry

I don't think I believe that. It's ok to have two different names.

 

[chrystal21]

No I did NOT guess! geez, its not good to assume. bc if thats the case then I'm assuming that nobody can help me on these type of problems??? It doesn't take much to show a person at least the first couple of steps then in getting the right answer.

 

[galactus]

I'll help with #2. Incidentally, your answer is incorrect.

Rationalize the denominator by multiplying by its conjugate.....and remember \(\displaystyle i^{2}=-1\)

\(\displaystyle \L\\\frac{4-2i}{3+5i}\cdot\frac{3-5i}{3-5i}\)

\(\displaystyle \L\\\frac{12-26i+10i^{2}}{9-25i^{2}}\)

Since \(\displaystyle i^{2}=-1\)

\(\displaystyle \L\\\frac{2-26i}{34}\)

This equals:

\(\displaystyle \L\\\frac{1}{17}-\frac{13}{17}i\)

It may help to remember the properties of i:

\(\displaystyle i^{2}=-1\)

\(\displaystyle i^{3}=-i\)

\(\displaystyle i^{4}=1\)

\(\displaystyle i^{5}=i\)

\(\displaystyle \underbrace{i^{6}=-1}\)

See, the pattern starts repeating.

 

[stapel]

1) Simplify i⁴².
Your answer of "1" is incorrect.

2) Simplify 4 - 2i/3 + 5i
It is difficult to comment on your answer, since your formatting is ambiguous. Did you mean "4 - (2i/3) + 5i" as you posted, or did you mean "(4 - 2i)/(3 + 5i)", or something else?

3) Subtract: (9 - 6i) - (-7i - 5)
Your answer of "14 + i" is correct.

4) Simplify \(\displaystyle \sqrt{-243}\)
Your answer of \(\displaystyle "9i\,\sqrt{3}"\) is correct.

5) Solve x = ...
Your formatting is again ambiguous, and there are many options as to your meaning. I hesitate to guess.

No I did NOT guess! geez... It doesn't take much to show a person at least the first couple of steps....

By the same reasoning, "it doesn't take much to show a person" your work.

The tutors already know how to do this. If you're asking if you did these correctly, please reply showing what you did.

Thank you.

Eliz.

 

[Mrspi]

Hello! I am new, and would like to know if anybody can PLEASE check and see if I have the right answers, and if wrong can somebody please help me find the correct one? Thank you!!


3) Subtract: (9-6i) - (-7i-5)
a) 4-13i
b) 4+i
c) 14-13i
d) 14+i
*I chose choice d, is that correct?

4) express in terms of i and simplify: Square root of -243
a) 9i square root 3
b) 12 square root 2i
c) 9 square root 2i
d) -12 square root 2i
* Choice A

5) Find one of the solutions of x= square root of 2x-6 +3
a) -6
b) 8
c) -3
d) 5

Ok, for problem 3 your answer is correct.

For problem 4, your answer is also correct.

For problem 5, I have NO idea what this means.

Is it
x = sqrt(2x - 6) + 3
or is it
x = sqrt(2x - 6 + 3)

We can't be expected to guess what you mean when you type a problem in such a way that there are multiple interpretations. Please repost this problem so that we can see clearly what is under the radical sign.

Please don't think we are being "mean" here....we can only help you if we see the problem in its correct context, and if we can see what you have done to solve the problem yourself.

Personally, I don't like these "multiple choice" type exercises, as it seems to me that this encourages wild guesses without requiring a student to do, or show, any work in the pursuit of a solution.