Question

大佬们，这些题怎么做？七年级的方法

Answer 1

一(1)原式=-1 - 0.5×(1/3)×(1-4)
=-1 - 0.5×(1/3)×(-3)
=-1 + 0.5
=-0.5
(2)原式=1 + (-18)×(2/9) - (-2)
=1 - 4 + 2
=-1

追答

(1)原式=5a²b-5ab²-5-ab²-3a²b+5
=(5-3)a²b - (5+1)ab² + (5-5)
=2a²b - 6ab²
=2ab(a - 3b)
=2×(-2)×(-1/2)×[(-2) - 3×(-1/2)]
=2×(-2 + 3/2)
=2×(-1/2)
=-1
(2)原式=3x²y-(2xy²-2xy+3x²y+xy)+3xy²
=3x²y-2xy²+xy-3x²y+3xy²
=(3-3)x²y+(3-2)xy²+xy
=xy²+xy
=xy(y+1)
=-3×(-2)×(-2+1)
=-6

(1)两边同乘6得：
3x - (5x+11)=6 + 2(2x-4)
3x-5x-11=6+4x-8
-2x-4x=-2+11
-6x=9
∴x=-3/2
(2)两边同乘12得：
4(7x-1) - 6(5x+1)=24 - 3(3x+2)
28x-4-30x-6=24-9x-6
-2x+9x=18+10
7x=28
∴x=4