19.(8分)化简:
(1)$(4a^{2}b-5ab^{2})-(3a^{2}b-4ab^{2})$;
(2)$x-[3x-2(1+2x)]$;
(3)$(7m^{2}n-5mn)-(4mn^{2}-5mn)+5m^{2}n$;
(4)$(b+3a)+2(3-5a)-(6-2b)$.
(1)$(4a^{2}b-5ab^{2})-(3a^{2}b-4ab^{2})$;
(2)$x-[3x-2(1+2x)]$;
(3)$(7m^{2}n-5mn)-(4mn^{2}-5mn)+5m^{2}n$;
(4)$(b+3a)+2(3-5a)-(6-2b)$.
答案:
(1)a²b-ab²;(2)2x+2;(3)12m²n-4mn²;(4)3b-7a
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