ABCD is a rhombus on a graph. B(7,10). AC: y=7-4x. Find an equation for DB in the form tx+py+r=0 where t,p&r are integers.

AC and DB must be perpendicular therefore m₁m₂ = -1. (we can work out the gradient of DB)-4m₂ = -1 -----> m₂ = 1/4The equation of a line is y-y₁=m(x-x₁) (sub in x, y and gradient values)y - 7 = 1/4(x-10) (multiply by 4 to get rid of fractions)4y - 28 = x -10 (make = to 0)x - 4y + 18 = 0