引用第2樓影於2006-09-27 20:47發表的“”:
thx~答案岩左
但點解@o@
Let x be the years time that Peter's age will be 1/4 of his grandfather's age
(12+x)=(63+x)/4(peter而家個age再加個年數就等於grandfather個age加年數,peter就係1/4 age of grandfather)
(12+x)x4=(63+x)/4x4
48+4x=63+x
48=63+x-4x
48-63=x-4x
-15=-3x
-15/-3=x
5=x
x=5
"After 5 years , Peter's age will be 4分1 of his grandfather's age.
b.)
Let x be the year time that grandfather's age 18 time Peter's
63-x=(12-x)x18(grandfather係63歲,x年前係peter既18倍,)
63-x=216-18x
63-216=-18x+x
-153=-17x
x=-153/-17
x=9
"9 years ago , grandfather's age was 18 times of Peter's age
[ 此貼被~瘋人~在2006-09-27 21:41重新編輯 ]