# matricies helpWatch

This discussion is closed.
Thread starter 14 years ago
#1
What exactly do i have to do for this question?
find the inverse?

If

A =
[1 5]
[0 1]

and

B=
[2 6]
[0 2]

find a 2 by 2 matrix X such that
A·X = B.
Also i think there is a dot inbetween matrcies A and B

Cheers
0
14 years ago
#2
Let X =
[a b]
[c d]

then A.X =

[1 5][a b] = [a+5c ... 5b+5d] = [2 6]
[0 1][c d]....[c ...........d ... ] ... [0 2]
=>c=0, d=2, a=2, b=-4/5
0
Thread starter 14 years ago
#3
(Original post by [email protected])
Let X =
[a b]
[c d]

then A.X =

[1 5][a b] = [a+5c ... 5b+5d] = [2 6]
[0 1][c d]....[c ...........d ... ] ... [0 2]
=>c=0, d=2, a=2, b=-4/5
Does this therefore mean that

X=
[2 6]
[0 2]
because this answer is not right...
0
14 years ago
#4
No, it means X=
[2 -4/5]
[0 2]
whats the answer say?
0
14 years ago
#5
(Original post by manps)
Does this therefore mean that

X=
[2 6]
[0 2]
because this answer is not right...
No B = (2,6,0,2) I believe [email protected] said X = (2,-4/5,0,2).

Euclid
0
14 years ago
#6
(Original post by manps)
Does this therefore mean that

X=
[2 6]
[0 2]
because this answer is not right...
No, it means that X =
[a b]
[c d]

With values of a,b,c,d given in her post
0
Thread starter 14 years ago
#7
(Original post by [email protected])
No, it means X=
[2 -4/5]
[0 2]
whats the answer say?
I'm doing this on Maple and it says this answer is not correct
0
14 years ago
#8
[1 5][a b] = [a+5c ... b+5d] = [2 6]
[0 1][c d]....[c ...........d ... ] ... [0 2]
=>c=0, d=2, a=2, b=-4
better?
0
Thread starter 14 years ago
#9
(Original post by [email protected])
[1 5][a b] = [a+5c ... b+5d] = [2 6]
[0 1][c d]....[c ...........d ... ] ... [0 2]
=>c=0, d=2, a=2, b=-4
better?
much much better
Thanks kt
0
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