1.{x/2=y/3 3x+4y=92.{4x-3y=-4 x/4+y/3=63.{(2x-1)/5+(3y-2)/4=2 (3x+1)/5-(3y+2)/4=0在等式y=kx+b中,当x=1时,y=-2时;当x=-1时,y=-4,求k、b的值.
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1.
{x/2=y/3 3x+4y=9
2.
{4x-3y=-4 x/4+y/3=6
3.
{(2x-1)/5+(3y-2)/4=2 (3x+1)/5-(3y+2)/4=0
在等式y=kx+b中,当x=1时,y=-2时;当x=-1时,y=-4,求k、b的值.
1.
x/2=y/3 (1)
3x+4y=9 (2)
由(1)
x=2y/3
代入(2)
3*2y/3+4y=9
6y=9
y=3/2
x=2y/3=1
2.
4x-3y=-4 (1)
x/4+y/3=6 (2)
(1)+(2)*9
4x-3y+9x/4+3y=-4+54
25x/4=50
x=8
y=(4x+4)/3=12
3.
(2x-1)/5+(3y-2)/4=2
两边乘20
8x-4+15y-10=40
8x+15y=54 (1)
(3x+1)/5-(3y+2)/4=0
两边乘20
12x+4-15y-10=0
4x-5y=2 (2)
(1)-2*(2)
25y=50
y=2
x=(54-15y)/8=3
在等式y=kx+b中,
当x=1时,y=-2
-2=k+b (1)
当x=-1时,y=-4
-4=-k+b (2)
(1)+(2)
-6=2b
b=-3
k=-2-b=1
(x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)=
2(x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15
x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20
{(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20
4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6
3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2
(x+y)/2- x-y/2=6 3(x+y)=4(x-y)
x+y/3+x-y/2=6 4(x+y)-2(x-y)=40
4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
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