Math Is Fun Forum

4littlepiggiesmom

Member

Registered: 2006-01-09

Posts: 42

Misc Math Problems

My daughter had to go to  music festival today so missed math test. she worked all weekend on the and asked me to look them over which I did but some of these  were over my head...so I came here.

1. What is the average rate of change of f(x)=x^3-x in the interval {-2,2}?
a. 6
B. -3   THIS is her answer!
c. 3
d. 0
e. none of these

2. If a+bi is a complex number, llet {a+bi}=(sqrt)a^2+b^2. What is n[(3+4ai)^3]?
a. 625
b.125
c.5
d. (sqrt)91 which is 9
e. none of these   THIS is her answer!!!

3. What is the sum of the solutions of 4^x -3 *2^x=2 + 32=0?
a. log^UNDERSCORE 2 (8/3)
b.2  THIS is her answer!
c. 5
D. -5
e. none of these

4. X+Y+Z, wher (x,y,z) is the solutionto the following linear  system:
X+2Y+3Z=1
Y+2Z=2
Z=3

a. 7 This is her answer
b. 9
c.0
d. 1
e. none of these

5.Simplify the expression ln(81)+lm(27)+in(9) all over /  ln(27)-ln(9) + ln (3)

a. ln(117)/lm(21)
b. 9/2
c. 7ln(3)  This is here answer
d. 4.51
e. none of these

hope I wrote these so you can understand them...thanks!

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Misc Math Problems

1 i guess is 3 instead of -3  3 = ((8-2) - (-8+2))/(2-(-2))
4 -1 (x+2y+3z)-(y+2z)=x+y+z
5 9/2 = (4+3+2)ln3 / [(3-2+1)ln3]

sorry i can't understand 2 and 3

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X'(y-Xβ)=0

4littlepiggiesmom

Member

Registered: 2006-01-09

Posts: 42

Re: Misc Math Problems

#2 should be this..
if a + bi is a complex number, let n[a+bi] = Sqrt (s^2 + b^2). What is n[(3+4i)^3]?

Answers
a. 625
b. 125
c. 5
d. Sqrt (91)
e. none of these

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Misc Math Problems

I guess a+bi is any complex number, and n[]is a kind of function that outputs a comlex number's modulus
|a+bi|=Sqrt (a^2 + b^2)
|(3+4i)^3| = |3+4i|^3 ( proven by polar form)=5^3

The answer is b

Last edited by George,Y (2006-03-16 15:00:58)

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X'(y-Xβ)=0