Question

Solve this system of equations using elimination.
-3x-4y=7
-2x+4y=3

x=
y=

Answer 1

If \[\text{ -3x-4y=7 }\] and
\[\ -2x+4y=3\] are true, then
\[\text{ -6x-8y=14 }\] and
\[\ -6x+12y=9\] are also true (multiplied by 2 and 3 respectively)

Answer 2

Therefore \[\ -6x=8y+14\] and \[\ -6x=-12y+9\] (re-arranging). So:
\[\ -12y+9=8y+14\]
You can find y using normal algebra now. Insert the found value for y into one of the first 2 equations, then find x.

Answer 3

Or you can add the two equations together and get -5x=10.

Answer 4

henpen's method is correct, but needlessly complicated and is not an example of the elimination method; it is an example of substitution via multiplication and the reflexive property/transitive property.