If one of the roots of 35x7x7x53=0 is –10, then other roots are:

35x7x7x53=0⇒3(3x−35)−5(21−7x)+x(35−x2)=0 ⇒9x−105−105+35x+35x−x3=0⇒x3−79x+210=0⇒(x+10)(x2−10x+21)=0⇒(x+10)(x−3)(x−7)=0⇒x=−10,3,7