第 11 楼
以下是引用zhady在2011-10-9 15:11:00的发言：
一開始約左4佢啦-.-
(10+x)(8+x)=80+63
x^2+18x+80=80+63
x^2+18x-63=0
(x+21)(x-3)=0
x=3 or x=-21(rejected)
GD
一開始約左4佢啦-.-
(10+x)(8+x)=80+63
x^2+18x+80=80+63
x^2+18x-63=0
(x+21)(x-3)=0
x=3 or x=-21(rejected)
GD
唔得...A SIR話要用因式分解先,用唔到先用公式法-.-如果唔係扣分,上次都扣左我分
前面2個抽左出黎既2係乘埋
即係2(10+x)2(8+x)
=4(10+x)(8+x)
let x and y be the length and width respectively,
xy=1200 ...(1)
x+2y=100 ...(2)
From (2), x=100-2y ...(3)
sub (3) into (1),
(100-2y)y=1200
2y^2-100y+1200=0
y^2-50y+600=0
(y-20)(y-30)=0
y=20 or y=30
put y=20 into (1)
x=60
put y=30 into (1)
x=40
Therefore,when the length is 40, the width is 30. when the length is 60,the width is 20.
我唔知長度係咪真係長d果條叫長
let x and y be the length and width respectively,
xy=1200 ...(1)
x+2y=100 ...(2)
From (2), x=100-2y ...(3)
sub (3) into (1),
(100-2y)y=1200
2y^2-100y+1200=0
y^2-50y+600=0
(y-20)(y-30)=0
y=20 or y=30
put y=20 into (1)
x=60
put y=30 into (1)
x=40
Therefore,when the length is 40, the width is 30. when the length is 60,the width is 20.
我唔知長度係咪真係長d果條叫長
數學神手- -
好似上年有課係Solve the equation in two unknowns
做到變機械人
好似上年有課係Solve the equation in two unknowns
做到變機械人
好憎文字題...要自己諗個規律出黎,好似雜錦題咁...
