Question

1.已知3x=4+m,2y-m=5,用含x的代数式表示y为___.

Answer 1

1.

3x=4+m

m=3x-4

2y-m=5

2y-(3x-4)=5

2y-3x+4=5

2y-3x=1

2y=1+3x

y=(1+3x)/2

2.

y=kx+b中,当x=2时y=-1,当x=-1时y=5

2k+b=-1

-k+b=5

k=-2

b=3

3.

|x+2y|+(x-y+1)²=0

x+2y=0

x-y+1=0

x+2y=0

x-y=-1

x=-1/3

y=2/3

(x+y)²=(-1/3+2/3)²=(1/3)²=1/9

4.

4x+3y=21

4kx+(k-1)y=4

解互为相反数

x+y=0

4x+3y=21

x=21

y=-21

4kx+(k-1)y=4

84k-21(k-1)=4

84k-21k+21=4

63k=-17

k=-17/63

5.

ax-by=4

2x+3y=4

ax+by=2

4x-3y=-10

2x+3y=4

4x-3y=-10

x=-1

y=2

ax-by=4

ax+by=2

-a-2b=4

-a+2b=2

a=-3

b=-1/2