（1）5x^4+3x^2y-10-3x^2y+x^4-1
=5x^4+x^4+3x^2y-3x^2y-10-1
=6x^4-11
(2)p^2+3pq+6-8p^2+pq
=p^2-8p^2+3pq+pq +6
=-7p^2+4pq +6
(3)(7y-3z)-(8y-5z)
=7y-3z-8y+5z
=7y-8y-3z+5z
=-y+2z
(4) -(a^5-6b)-(-7+3b)
= -a^5+6b+7+3b
= -a^5+6b+3b +7
= -a^5+9b +7
(5)2(2a^2+9b)+3(-5a^2-4b)
=4a^2+18b-15a^2-12b
=4a^2-15a^2+18b-12b
=-11a^2+6b
(6)-3(2x^2-xy)+4(x^2+xy-6)
=-6x^2+3xy+4x^2+4xy-24
=-6x^2+4x^2+3xy+4xy-24
=-24x^2+7xy-24