✔ 最佳答案
1. Simplify (3r-s)^2/12r-4s
(3r-s)^2/12r-4s
=(3r-s)^2/4(3r-s)
=(3r-s)/4
2.Use simultaneous equation:
y=5x+2=6x+3
5x+2=6x+3
x=-1
Sub x=-1 into y=5x+2
y=-3
so,x=-1,y=-3
3.Use simultaneous equation:
x=3/4y+1=1/2y+3
{x=3/4y+1
{x=1/2y+3
Sub x=3/4y+1 into x=1/2y+3
3/4y+1=1/2y+3
3y+4=2y+12
y=8
Sub y=8 into x=3/4y+1
x=7
So,x=7,y=8
4.Use the method of substitutation and the method of elimination.
{r+5s=2 --------------(1)
{4r-3s=31----------------(2)
From(1),
r+5s=2
r=2-5s----------------(3)
sub (3) into (2)
4(2-5s)-3s=31
8-20s-3s=31
-23s=23
s=-1
Sub s=-1 into (3)
r=2-5(-1)
r=7
so,r=7,s=-1
5.A metal rod of length 0.5m expands to 0.535m when the temperature is increased from 25℃to 165℃. Find the rate of expansion in mm/℃.
the increase of length:(0.535-0.5) x 1000 mm=35 mm
the increase in temperature:(165-25)*C=140*C
The rate of expansion:
= 35/140 mm/*C
=1/4 mm/*C
The required answer is 1/4mm/*C
2007-01-04 19:54:33 補充:
For question(5),the answer can also be written as 0.25mm/*C