If x2+ax+10=0 and x2+bx-10=0 have a common root, then a2-b2 is equal to ___.

Let α be a common root, thenα2+aα+10=0    ...(i)and α2+bα-10=0    ...(ii)from (i)-(ii)(a-b)α+20=0⇒α=-20a-bSubstituting the value of α in (i), we get(-20a-b)2+a(-20a-b)+10=0 ⇒400-20a(a-b)+10(a-b)2=0⇒40-2a2+2ab+a2+b2-2ab=0  ⇒a2-b2=40