is this equation a direct variation? 8x + 9y = 10if it is what is the constant of variation?

Expert Answers
lfryerda eNotes educator| Certified Educator

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.