f.1 math

(a)
(-2/3)-(-5/6)
= -2/3+5/6
= -4/6+5/6
= (-4+5)/6
= 1/6

(b)
(-10/3)x(-9/4)
= (10/3)x(9/4)
= (10/1)x(3/4)
= (5/1)x(3/2)
= 15/2

(c)
(-25/4)/(5/2)
= (-25/4)x(2/5)
= (-5/4)x(2/1)
= (-5/2)x(1/1)
= -5/2

(d)
[ (-2)x(-5)x(+4) ] / [ (+3)x(-4)x(-8) ]
= [ (10)x(+4) ] / [ (-12)x(-8) ]
= (40) / (96)
= 5/12

2.
-(25/4)=(5/-2)x
(25/4)=(5/2)x
(5/4)=(1/2)x
(5/2)=(1/1)x
5/2=x
x = 5/2

步步做比你,自己跟下,應該明白

2007-07-22 21:35:12 補充：
第二條我做你係 -(25/4)=(5/-2)x而唔係 -(25/4)=5/(-2x)你打少個括號或者括住邊度,係好大分別自己諗下,又好似第一題 d 部, 應該又係打少括號,我做係上面三個數除下面三個數[ (-2)x(-5)x(+4) ] / [ (+3)x(-4)x(-8) ]