P.6升F.1 英文數(方程)

1)(a)
The total amount of money =$5X2x+$2Xx=$12x+$2x=14x
If the total amount of money is $14,then x = 1.

(b)
The number of coins he has= 2x+x =3x
If the number of coins is 6,then x = 2.

少左個句子呀！If x=3 and y =5
2)4x+3y/2xy
=4(3)+3(5)/2(3)(5)
=12+15/30
=27/30
=9/10

3)
y/x+1 + x/y+1
=(5/3+1)+(3/5+1)
=5/4+3/6
=15/12+6/12
=21/12
=7/4

4.
xy+1/x-1 + (x+1)y/y-1
=[(3)(5)+1/3-1]+[(3+1)5/5-1]
=16/2+20/4
=8+5
=13
我都有e本暑期作業，所以我知少左個句子。

2007-08-14 16:57:39 補充：
1)(a)Peter has 2x five-doller coins and x two-doller coinsPeter has $ 5 X 2x $2 X x = $12x $2x = 12xIf the total amount of money is $12,then x = 1.(b)By adding one condition,find a possible value of x.If the number of coins he has = 2x x = 3xIf the number of coins is 6,then x= 2 .

1(a)
The total amount of money = 2x*5+2x = 12x
If the total amount of money is $24,then x = 2.

(b)
The number of coins = 2x+x =3x
If the number of coins is 3,then x = 1.

2.
4x+3y/2xy = 4x+3/2x // (8x+3)/2x

3.
y/x+1 + x/y+1 = (y(y+1)+x(x+1))/(x+1)(y+1) // (y^2+y+x^2+x)/(x+1)(y+1)

4.
xy+1/x-1 + (x+1)y/y-1
= ( xy(x-1)(y-1)+(y-1)+(x+1)(x-1)y ) / (x-1)(y-1)
= ( (x^2y-xy)(y-1)+(y-1)+(x^2-1)y ) / (x-1)(y-1)
= (x^2y^2-xy^2+xy-1)/(x-1)(y-1) // ( (xy)(xy-y+1)-1 ) / (x-1)(y-1)