Question

先合并同类项再计算 求代数式的值

求代数式的值
6x+2x^2-3x+x^2+1 其中x= -5
4x^2+3xy-x^2-9 其中x=2 y= -3
1/3m-3/2n-5/6n-1/6m 其中m=6 n=2
3pq-4/5m-4pq 其中m=5 p=1/3 q=-3/2

要求具体 要步骤

Answer 1

6x+2x^2-3x+x^2+1
=2x^2 +x^2+6x-3x+1
=3x^2+3x+1
=3×（-5）^2+3×（-5）+1=61
4x^2+3xy-x^2-9
=4x^2-x^2+3xy-9
=3x^2+3xy-9
=3×2^2+3×2×（-3）-9=-15
1/3m-3/2n-5/6n-1/6m
=1/3m-1/6m -3/2n-5/6n
=1/6m -7/3n
=1/6×6-7/3×2
=-11/3
3pq-4/5m-4pq
=3pq-4pq-4/5m
=-pq-4/5m
=-1/3×（-3/2)-4/5×5
=-7/2=-3又2分之1

Answer 2

6x+2x^2-3x+x^2+1 其中x= -5
= 3x^2 + 3x +1
= 3*25 + 3*5 +1
=91

4x^2+3xy-x^2-9 其中x=2 y= -3

= 2x^2 +3xy -9
= 2*4+ 3*2*(-2)-9
=-13

1/3m-3/2n-5/6n-1/6m 其中m=6 n=2

=1/6*m-7/3*m
=1/6*6-7/3*2
=-1/6

3pq-4/5m-4pq 其中m=5 p=1/3 q=-3/2
= -pq -4/5m
= -(1/3)*(-3/2)-4/5*5
= -9/2