中一數學(請詳列步驟)

[匿名]

2011-04-22 4:55 pm

1. Does P(2，7) lie on the graph of y=5x–3

2. If M(–4，m) lies on the graph of 4x+3y+7=0，

find the value of m

3. It is given that 2a=3b=4c，where a，b and c are non-zero. Find a：b：c

4. A car travels 90km in 45 minutes. Find the speed of car

(a) in km/h (b) in m/s

5 . It is given that the scale of a map is 1：20 000. Find the actual distance for a distance of 12.5 cm on the map

6. If 1/x+y=1 or 1/x+z=1 .Find the value of 1/y+z

更新1:

最好能在4月24日或之前回覆，thanks！

回答 (1)

良師益友

2011-04-23 5:34 am

✔ 最佳答案

Answers as follows:

1) Put x = 2:

y = 5(2) - 3 = 7

Hence ( 2, 7 ) satisfies the eq. y = 5x - 3

Hence, ( 2, 7 ) lies on it.

2) Put ( x, y ) = ( -4, m ):

4( -4 ) + 3( m ) + 7 = 0

3m = 9

m = 3

3) LCM ( 2, 3, 4 ) = 12

Hence, 2a/12 = 3b/12 = 4c/12

a/6 = b/4 = c/3

Hence, a : b : c = 6 : 4 : 3

4) Speed of the car

= 90 km / ( 3/4 hr )

= 120 km / hr

= 120 ( 1,000 m ) / ( 3,600 s )

= 100/3 m/s

5) Actual Dist.

= 12.5 cm x 20,000

= 250,000 cm

= 2,500 m

= 2.5 km

6) ( I suspect if you have typed the Qn wrongly but I still try to answer from my understanding )

1/( x + y ) = 1 = 1/( x + z )

Hence, y = z and x + y = x + z = 1

Hence, 1/ ( y + z ) = 1/2y or 1/2z

( i.e. no more can be simplified )

Hope I can help you.

參考: Mathematics Teacher Mr. Ip

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