What is the correct option?

sample paper nest-juniorsample paper nest-junior

2 Answers

Option (D) 9I-A9IA is correct

Explanation:

Find A^{-1}=\frac{\adj(A)}{|A|}A1=adj(A)|A|

Check the options. Option (D) satisfies the given condition

Jul 28, 2018

The answer is option (D)option(D)

Explanation:

The matrix is

A=((2,-3),(-4,7))

The inverse of a matrix

A=((a,b),(c,d)) is

A^-1=1/(det A)((d,-b),(-c,a))

The determinant of

|A|=ad-bc=2*7-(-3*-4)=14-12=2

Therefore,

A^-1=1/2((7,3),(4,2))

And

2A^-1=((7,3),(4,2))

9I-A=9((1,0),(0,1))-((2,-3),(-4,7))

=((7,3),(4,2))

=2A^-1

The answer is option (D)