(1)化简:3(m2﹣2m﹣1)﹣2(m2﹣3m)
(2)先化简,再求值:3(﹣x+2y2)﹣2(3x﹣y2)+6x,其中x=﹣1,y=﹣2
(2)先化简,再求值:3(﹣x+2y2)﹣2(3x﹣y2)+6x,其中x=﹣1,y=﹣2
下列运算:①2a+3b=5ab;②3m2n-2nm2=m2n;③a-(b-c)=a-b+c;④y-x=-(x-y);正确的个数是( )
A.1 | B.2 | C.3 | D.4 |
A.1 | B.2 | C.3 | D.4 |