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**please help me prove this....**

## Homework Statement

Show that If "A" is an n-rowed matrix that satisfies A^2=A Then:

Row(A)+Row(I-A)=n

## Homework Equations

## The Attempt at a Solution

well since A is n-rowed that means that its an n*n matrix so Ax=I

as i guess so :

Row(A)=Rank(A)

Rank(I-A)+nullity(I-A)=Rank(A)+nullity(A)=n

plz help if i find its solution I will be given 20 mark for it and i have been trying to solve it for over two day :S