quadratics

y=(0.4x+2)(x-9)   .......this is pretty easy......to find the roots, just set both factors = 0.......so we have...

0.4x + 2   = 0     subtract 2 from both sides

0.4x  = -2         divide both sides by  0.4

x =  -5

And

x - 9  =  0     add 9 to both sides

x = 9

So....the two roots are   x = -5   and x  = 9