A line that is a direct variation must be of the form y=mx, where m is the slope of the line. This means, for the line 8x+9y=10, to determine if it is direct variation, then we need to rearrange it by isolating y.
`8x+9y=10` move 8x term to right side
`9y=-8x+10` divide both sides by 9
In this case, we see that the slope is `-8/9` , but there is a non-zero y-intercept, since `b=10/9` .
The line is a partial variation, and is not a direct variation.