1.若x^2+2x=3,則x^4+7x^3+8x^2-13x+15=
2.已知當a=-2時,代數(shù)式ax^3+bx+1的值為3,那么當x=2時,ax^3+bx-2=
3.設m和n均不為0,3x^2y^3和-6x^(2+2m+n)y^3是同類項,則2m^3-3m^2n+mn^2+7n^3/4m^3+2m^2n-5mn^2+7n^3=
4.當m=2π時,多項式am^3+bm+1的值是0,則多項式4aπ^3+bπ+5.5=
5.若a+b+c=30,3a+b-c=50,b、c均為非負數(shù),試求x=5a+4b+2c的取值范圍.
6.已知多項式x^2+ax-y+b和bx^2-3x+6y-3的差的值與字母x的取值無關,求代數(shù)式3（a^2-2ab-b^2)-2(2a^2-ab+b^2)的值.
急啊…………………………