中一MATHS:方程式

7-0.5[x-0.2(6-x)]=3x+22
7-0.5[x-1.2+0.2x]=3x+22
7-0.5x+0.6-0.1x=3x+22
-0.6x+7.6=3x+22
3.6x=-14.4
x=-4

2006-10-22 03:35:33 補充：
rac1ai:1) 7-0.5[x-0.2(6-x)]=3x+222) 7-0.5[x-1.5-0.2x]=3x+223) 7-0.5x-0.75-0.01x=3x+224) 6.25-0.51x=3x+225) 6.25=2.51x+226) 6.25-22=2.51x+22-227) 15.75=2.51x8) x=5

2006-10-22 03:35:50 補充：
1) -0.2*6 is equal to -1.21) -0.2*-x is equal to 0.2x2) -0.5*-1.5 is equal to 0.752) -0.5*-0.2x is equal to 0.1x4) 　　　　6.25-0.51x=3x+22　　6.25-0.51x+0.51x=3x+0.51x+22　　　　　　　　6.25=3.51x+226) 6.25-22 is equal to -15.757) 15.75/2.51 is not equal to 5

2006-10-22 03:40:04 補充：
u need some revision on this+ value * +value =+value+value * -value + -value-value * -value = +value

2006-10-22 19:03:33 補充：
samchow0226:其實每當你遇見這樣問題都用這樣的step 就可以了1) 拆括號2) 先處理加減(記得有一樣的末知數先可以一起加和減)3) 把有一樣的末知數放在一起(記得如果是從一邊帶到別一邊加變減,減變加)4) 最後處理乘除

the answer is 錯

7-0.5[x-0.2(6-x)]=3x+22
7-0.5(x-1.2+0.2x)=3x+22
7-0.5(1.2x-1.2)=3x+22
7-0.6(x-1)=3x+22
7-0.6x+0.6=3x+22
76-6x=30x+220
36x=-144
x=-4

7-0.5[x-0.2(6-x)]=3x+22
=7-0.5[x-1.5-0.2x]=3x+22
=7-0.5x-0.75-0.01x=3x+22
=6.25-0.51x=3x+22
=6.25=2.51x+22
=6.25-22=2.51x+22-22
=15.75=2.51x
x=5