中一數學help(升中的暑期作業)

1.X=54

2.(7a-23)/6

3.vt m

4.6(x^2)-8x

5.36m-4m^2

6.-6

7.2

希望幫到你

1. 兩個數的H.C.F和L.C.M分別是6和108,若該兩個數是12和X,求x的值
HCF = 2 x 3; LCM = 2 x 2 x 3 x 3 x 3
12 = 2 x 2 x 3; 所以 X = 2 x 3 x 3 x 3 = 54


2. 5(a-1)/2 - 4(a+1)/3
= 5a/2 - 5/2 - 4a/3 - 4/3 [拆括號]
= 5a/2 - 4a/3 - 5/2 - 4/3 = a(5/2 - 4/3) - 15/6 - 8/6
= a(15/6 - 8/6) - 23/6 = 7a/6 - 23/6
= (7a - 23)/6


3. 一輛汽車的速率是v m/s,在t秒內,汽車行駛多遠?
在 t 秒內,汽車行駛 vt meter


4. 2x(3x - 4) = 6x2 - 8x
or 2 x (3x - 4) = 6x - 8



5. (9-m)(4m) = 36m - 4m2


6. (-2)(-3)(+4)-(-5)(-6) = (+6)(+4)-(+30) = 24 - 30 = -6

7. (-4)(-6)-(-5)(+8)/(-5)(+2)-(-2) = (+24)-(-40)/(-10)-(-2)
= (+24)-(+4)+2 = 24 - 4 + 2
= 22

2008-07-27 13:38:07 補充：
7. (-4)(-6)-(-5)(+8)/(-5)(+2)-(-2) = (+24)-(-40)/(-10)-(-2)

= (+24)-(-40)/(-5)(+2)+2 = 24 - (+8)(+2) + 2

= 24 - 16 + 2

= 10

原本的答案有錯，Sorry。

2008-07-27 13:40:03 補充：
最後補充

7. (-4)(-6)-(-5)(+8)/(-5)(+2)-(-2)

= (+24)-(-40)/(-5)(+2)+2

= 24 - (+8)(+2) + 2

= 24 - 16 + 2

= 10