Name:
Lab # 8
October 21, 2015
The lab is due by start of lab on October 28, 2015.
A usefull aspect of a spreadsheet is the ability to work with matrices. Adding, subtracting, and multiplying a matrix by a number are operations that are fairly standard in terms of formulas with cells. write
the formula for the first element and then copy and paste.
The spread sheet also has the commands in the array category of the function wizard to work with
matrices: MINVERSE and MMULT
Problem 1. Use these matrices to do the following computations.

20

A =  −19
2
27
−26
3

−1

1 
0

10

B= 1
2
5
6
9

0

9 
5

15

C =  −8
7
25
10
35

−5

1 
−4

2

D= 5
3
8
2
10

−1

10 
7
Do the following computations. Be sure to clearly label your answers in the spreadsheet. you do not
need to include these answers on this paper.
1. 2A + 3B − 6C
5. ABC
2. 3D − 4A + 2B
6. A−1
3. AC
7. C −1
4. BD
8. A−1 ∗ B
Problem 2. Solve these systems of equations by using matrice inverses. Give your answers to at least
3 decimal digits. Do this problem on a different page of the spreadsheet. hint: look carefully at the
first two problems.
3x − 2y + 8z = −60
−2x + 2y + z = 25
x + 2y − 3z = 75
Answer: x =
y=
z=
y=
z=
y=
z=
3x − 2y + 8z = 49
−2x + 2y + z = −2
x + 2y − 3z = −16
Answer: x =
2x + y + 3z − 4w = 9
x + 2y + 3w = 1
x − 3z + w = 10
x−y−z−w =8
Answer: x =
w=
Once again e-mail me the spreadsheet showing how you solved these problems.