Math Help

Archive for November, 2010

Question: How to solve math logic problem?

If you put a coin on the first square of a checker board and then 2 on the next then 4 and just keep doubling the previous amount on all 64 squares, how many coins would be on the board when you finish?
My friend needs help with her logic class and she manually did this on her calculator and got the answer, but we wanted to know how you would generally solve this problem. Is there an equation for this?

Answer: When you add powers of two, you will get as a sum the next highest power of two minus one:
1 +2 +4 =7 =8 -1
1 + 2 +2^2 + … + 2^9 =2^10 – 1
So for the checkerboard problem, the answer is 2^64 -1.

Math Fractions & Equations : How to Solve Logic Problems

Question: any math majors? Matrices help?

so i understand how to add, subtract, and multiply Matrices ex: AB, A+B, A-B but I really don’t understand how to get the inverse. a step-by-step would really help out

Answer: for a 2×2 matrix
a b
c d
you just divide the matrix
d -b
-c a
by the determinant (ad-bc).

For a 3×3 matrix
a b c
d e f
g h i
calculate the matrix
a* b* c*
d* e* f*
g* h* i*
where these nine numbers are
(ei-fh) (ch-bi) (bf-ce)
(fg-di) (ai-cg) (cd-af)
(dh-eg) (bg-ah) (ae-bd)
[notice the pattern - each of these matrix elements is the determinant of a 2x2 matrix got by crossing out a row and a column in the original matrix]. This new matrix is called the ‘adjoint’ matrix.
Now divide the ‘adjoint’ matrix throughout by the determinant of the original matrix, which is
(aa* + bb* + cc*),
and you’ve got the inverse of
a b c
d e f
g h i

It’s tricky (you have to be very careful with the minus signs!).

The method generalizes for nxn Matrices. I hope you don’t want me to go into that (-:

Math Lessons : Solving a Matrix

Question: I need help with my math homework????!!?? (Slope intercept form)?

I was wondering if someone could help me understand this math problem..
Find the equation of a line (in slope-intercept form) passing through two points….show all work. (find the slope first, then use point-slope form. Fill in the slope and the X1, Y1. Then distribute and get y by itself. Done)
23.) A(4,9) and B(-2,-3) 24.) C(1,1) and D(-2,10)

Answer: To find slope intercept form you have to first find slope so pick any two points and do the equation
y2-y1/x2-x1

and that equals your slope
So now you just have to find your intercept and put it together

Converting to Slope-Intercept Form and Graphing – YourTeacher.com