Question

solve the linear system using elimination
4x-y=5
4x+4y=-4

Answer 1

are you formiliar with the "elimination" method?

Answer 2

no

Answer 3

okay so with this method we essentially add the two equations to each other and one of the variables cancels out

Answer 4

but in order for them to cancel we first need to prepare the equations so that they will

Answer 5

they will cancel only if you have the same number in front of the variable in each equation, except one is positive and one is negitve

Answer 6

in your example do oyu see how in the first equation we have 4x and in the second equaiton we also have a 4x?

Answer 7

Yeah

Answer 8

we need change one of those into a -4x for this to work

Answer 9

but!

Answer 10

we cant just change it to -4x

Answer 11

we need to multiply everything by -1

Answer 12

lets do it to the bottom one

Answer 13

if you multiply every term in the bottom equation by -1 what do you get?

Answer 14

-4x+-4y=4

Answer 15

correct!

Answer 16

Now we have: