Question

when working with matrices, and performing row operations, how to i determine which equations to keep the same

Answer 1

it depends on what your trying to accomlish

Answer 2

you usually want to get it into the form of an identity matris

100
010
001

Answer 3

like if i am trying to get into ro-ecelon form. Sometimes in my book they say add 2*row three to row 2, producing a new row 2

Answer 4

but why is it that we dont also get a new row 3

Answer 5

row echelon is just zeroing out the under on the pivots right?

Answer 6

right

Answer 7

the idea is to modify one row thru addition by using a useful form of the pivoting row; the pivoting row is already set so it doesnt need changed does it?

in this case that would have been row 2

Answer 8

so in the case i mentioned above the row 2 is not changed because its the pivoting row, meaning we are adding it to row 3

Answer 9

thus producing a new row three, but keeping the original row 2

Answer 10

correct; changing row 2 at some later point is fiine; but for your problem its not needed to change

Answer 11

alright, thanks

Answer 12

youre welcome :)