give the 2 numbers variables,say x and y. then they multiply to -225.this means xy=-225 they add to 16.this means x+y=16 y=16-x
substitute y=16-x onto xy=-225 to get x(16-x)=-225 then expand to get 16x-x^2=-225 rearrange to get a quadratic: x^2-16x-225=0 x=(16+(16^2-4*-225)^0.5))/2 or x=(16-(16^2-4*-225)^0.5))/2