4x - 5y = -18
3x + 2y = -2
To eliminate y, we observe the coefficients of y.
They are -5 and +2. If we ignore signs the least
common multiple of 5 and 2 is 10, so we multiply
the first equation through by 2 to make y have a
coefficient of -10 and the second equation by 5 to
make y have a coefficient of -10:
8x - 10y = -36
15x + 10y = -10
Then we add them vertically term by term:
8x - 10y = -36
15x + 10y = -10
———————————————
23x = -46
x = -2
Substitute -2 for x in
3x + 2y = -2
3(-2) + 2y = -2
-6 + 2y = -2
2y = 4
y = 2
The solution is (x,y) = (-2,2)
Edwin
