题目设A=−3b2+4ab+2cA=-3b^{2}+4ab+2cA=−3b2+4ab+2c,B=−2b2+2ab+2cB=-2b^{2}+2ab+2cB=−2b2+2ab+2c.(1)(1)(1)求2A−3B2A-3B2A−3B.(2)(2)(2)当bbb为111,222,444时,代数式2A−3B2A-3B2A−3B的值分别是mmm,333,nnn,求2m+n2m+n2m+n的值.知识点：整式化简求值章节：数与式 / 整式
