Algebra 1: Common Core (15th Edition)

Direct variation has the form y=kx. Thus, we need to simplify to isolate y to see if it is direct variation. Thus, we obtain: $4x+5y=0 \\\ 4x=-5y \\\\ y=-4/5x$ This does have the form y=kx, so it is direct variation. k is the constant of variation, so we know that the thing x is being multiplied by, -4/5, is the constant of variation.