The two original functions are 4x+9y=7 and 4x-9y=9
To use the combination method, add all the values of the two equations together to cancel out one of the variables
4x+4x+9y-9y=7+9
8x=16
8x/8=16/8
x=2
4(2)+9y=7
8+9y=7
8-8+9y=7-8
9y=-1
y=-
To use the combination method, add all the values of the two equations together to cancel out one of the variables
4x+4x+9y-9y=7+9
8x=16
8x/8=16/8
x=2
4(2)+9y=7
8+9y=7
8-8+9y=7-8
9y=-1
y=-