
Patrick B. answered 06/22/21
Math and computer tutor/teacher
First, the plural of MATRIX is MATRICES
will use STRONG INDUCTION to prove
the statement about this MATRIX
The statement clearly holds for N=1.
This is left for you to verify.
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For n=2, the entries of the MATRIX are:
1+6n=13 4(2) = 8
-9*2 = -18 1 - 6(2) = -11
and
[7 4] [ 7 4]
[-9 -5] [ -9 -5]
= [ 49-36 28-20 ]
[ -63+45 -36+25]
= [ 13 8]
[ -18 -11]
So the statement holds for these MATRICES when n=2
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For some natural number N, the Induction Hypothesis says
that is GIVEN
that A^n = [ 1 +6n 4n]
[ -9n 1 - 6n]
Then A^(n+1) = A^n*A =
*********** by substitution **************
[ 1+6n 4n ] [ 7 4 ]
[ -9n 1-6n ] [ -9 -5 ]
******** multiplies the MATRICES ***************
= 7(1+6n) - 9(4n) 4(1+6n) - 5(4n)
7(-9n) - 9(1-6n) 4(-9n) - 5(1-6n)
************* distributive *********************
= 7 + 42n - 36n 4 + 24n - 20n
-63n - 9 + 54n -36n - 5 + 30n
*********** combines like terms **********************
= [7 + 6n 4 + 4n]
[-9n - 9 -6n - 5]
****substitutes 7=6+1, factors out 4, factors out -9, and -5 = -6+1
= [ 1 + 6 + 6n 4(n+1) ]
[ -9(n+1) -6n - 6 +1 ]
******** factors out 6 and -6 from diagonal entries
= [ 1 + 6(n+1) 4(n+1)
-9(n+1) -6(n+1)+1
****** Let V = n+1 ***************************
= 1 + 6V 4V
-9V -6V+1
which is the exact same pattern in terms of V=n+1.
This completes the proof
No this was not easy at all.