2二次方-2三次方-2四次方-2五次方-2六次方-2七次方-2八次方-2九次方+2十次方
=2二次方-2三次方-2四次方-2五次方-2六次方-2七次方-2八次方＋2九次方
=2二次方-2三次方-2四次方-2五次方-2六次方-2七次方＋2八次方
=······
=2²＋2²
=8