[Sora]

How do I go about this? The mark scheme on the MEI website confused me.

Thanks,
Sora

[ghostwalker]

(Original post by Sora)


How do I go about this? The mark scheme on the MEI website confused me.

Thanks,
Sora

Since , what's in terms of ?

[Sora]

I'm not sure. Matrices is the only thing I don't understand in FP1.

[steve10]

I would just multiply A by all the options (a,b,c,d) until I got the identity matrix.

[ghostwalker]

(Original post by Sora)
I'm not sure. Matrices is the only thing I don't understand in FP1.

Perhaps if we rewrite it:



Hence

[Sora]

A^-1 = A^2 ?

[ghostwalker]

(Original post by Sora)
A^-1 = A^2 ?

Yep!

[Sora]

Not entirely sure how though. Can you explain please?

[ghostwalker]

(Original post by Sora)
Not entirely sure how though. Can you explain please?

From

we can premultiply each side of the equation by

So.



Thus, in detail:







Obviously, you wouldn't need to put all that detail in, in an answer; I've just included it for your understanding.

[Josephdude]

Is that A(A^-1) = I = A^3?

then A^-1 = A^2

[Sora]

Sort of get it now, thanks.

[Mr Tough]

Anyone done any work/learning on n x n matrices?