方程的简单变形 3x+4=03x=-4x=-4/37y+6=-6y7y+6y=-6y=-6/135x+2=7x+85x-7x=-2+8-2x=6x=-33y-2=y+1+6y3y-y-6y=2+1-4y=3y=-3/42/5x-8=1/4-0.2x2/5x+1/5x=1/4+83/5x=33/4x=55/41-1/2x=x+1/3-1/2x-x=-1+1/3-3/2x=-2/3x=118=5-x-x=18-5x=-133/4x+2=3-1/4x3/4x+1/4x=3-
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方程的简单变形 3x+4=03x=-4x=-4/37y+6=-6y7y+6y=-6y=-6/135x+2=7x+85x-7x=-2+8-2x=6x=-33y-2=y+1+6y3y-y-6y=2+1-4y=3y=-3/42/5x-8=1/4-0.2x2/5x+1/5x=1/4+83/5x=33/4x=55/41-1/2x=x+1/3-1/2x-x=-1+1/3-3/2x=-2/3x=118=5-x-x=18-5x=-133/4x+2=3-1/4x3/4x+1/4x=3-
方程的简单变形
3x+4=0
3x=-4
x=-4/3
7y+6=-6y
7y+6y=-6
y=-6/13
5x+2=7x+8
5x-7x=-2+8
-2x=6
x=-3
3y-2=y+1+6y
3y-y-6y=2+1
-4y=3
y=-3/4
2/5x-8=1/4-0.2x
2/5x+1/5x=1/4+8
3/5x=33/4
x=55/4
1-1/2x=x+1/3
-1/2x-x=-1+1/3
-3/2x=-2/3
x=1
18=5-x
-x=18-5
x=-13
3/4x+2=3-1/4x
3/4x+1/4x=3-2
x=1
3x-7+4x=6x-2
3x+4x-6x=7-2
x=5
10y+5=11y-5-2y
10y-11y+2y=-5-5
y=-10
a-1=5+2a
a-2a=5+1
-a=6
a=-6
0.3x+1.2-2x=1.2-2.7x
0.3x+2.7x-2x=1.2-1.2
x=0
2y+3=11-6y
2y+6y=11-3
8y=8
y=1
2x-1=5x+7
2x-5x=1+7
-3x=8
x=-3/8
1/3x-1-2x=-1
1/3-2x=1-1
x=0
1/2x-3=5x+1/4
1/2x-5x=3+1/4
-9/2x=13/4
x=-13/18
已知y1=3x+2,y2=4-x,
(1)当x取何值时,y1=y2?
3x+2=4-x
3x+x=4-2
x=1/2
(2)当x取何值时,y1比y2大4?
3x+2-(4-x)>4
3x+2-4+x>4
x>3/2
x>3/2时,y1比y2大4.
方程的简单变形 3x+4=03x=-4x=-4/37y+6=-6y7y+6y=-6y=-6/135x+2=7x+85x-7x=-2+8-2x=6x=-33y-2=y+1+6y3y-y-6y=2+1-4y=3y=-3/42/5x-8=1/4-0.2x2/5x+1/5x=1/4+83/5x=33/4x=55/41-1/2x=x+1/3-1/2x-x=-1+1/3-3/2x=-2/3x=118=5-x-x=18-5x=-133/4x+2=3-1/4x3/4x+1/4x=3-
1-1/2x=x+1/3
-1/2x-x=-1+1/3
-3/2x=-2/3
x=1
不对,最后一步错了,x=4/9
2x-1=5x+7
2x-5x=1+7
-3x=8
x=-3/8
也是最后一步错了,x=-8/3
(2)当x取何值时,y1比y2大4?
3x+2-(4-x)>4
3x+2-4+x>4
x>3/2
x>3/2时,y1比y2大4.
不对,应该是
3x+2-(4-x)=4
3x+2-4+x=4
x=3/2
x=3/2时,y1比y2大4.
对了
正负变号对了就对了
ok
对了 ....
1-1/2x=x+1/3
-1/2x-x=-1+1/3
-3/2x=-2/3
x=1 (应该是 x=4/9 )
2x-1=5x+7
2x-5x=1+7
-3x=8
x=-3/8 (应该是 x=-3/8)
(2)当x取何值时,y1比y2大4?
3x+2-(4-x)>4
3x+2-4+x>4
x>3/2
x>3/2时,y1比y2大4. (应该是 x=3/2 当x=3/2时,y1- y2=4)