化简求值 2m-(-3n+(4n-2(3m-n)+5n))其中m=-(1/2) n=-1已知A=3a^2-2a+1,B=5a^2-_数学解答

化简求值 2m-(-3n+(4n-2(3m-n)+5n))其中m=-(1/2) n=-1
已知A=3a^2-2a+1,B=5a^2-3a+2，求3A-2B

人气：143 ℃　时间：2019-10-09 12:16:29

解答

2m-(-3n+(4n-2(3m-n)+5n))
= 2m-(-3n+(4n-6m-2n+5n))
=2m-(-3n+4n-6m-2n+5n)
=2m+3n-4n+6m+2n-5n
=(2+6)m+(3-4+2-5)n
=8m-4n
=8x(-1/2)-4x(-1)
=-4+4
=0已知A=3a^2-2a+1,B=5a^2-3a+2，求3A-2B3A-2B=3(3a²-2a+1)-2(5a²-3a+2)=(9a²-6a+3)-(10a²-6a+4)=9a²-6a+3-10a²+6a-4=-a²-1