f1 solving the equation.....(math) 20marks!! 急!!!!!

你要分2個case先,因為連續數可以係遞進or遞減~
即係1,2,3,4...(遞進) 5,4,3,2...(遞減)~

第一個case (遞進)
let x be the first number of her tele.no.

x + x + x + x + (x+1) + (x+2) + (x+3) + (x+4) = (x+3)*(10) + (x+4)　　　　　 *=乘

(左手邊係所有字的和,右手邊係最後2個數字所構成的兩位數)

8x + 10 = 10x + 30 + x + 4
3x = -24
x = -8 which is impossible,so rejected. (因為冇可能係負數)


第2個case (遞減)

let x be the first number of her tele.no.

x + x + x + x + (x-1) + (x-2) + (x-3) + (x-4) = (x-3)*(10) + (x-4) 　　　　　　 *=乘

(左手邊係所有字的和,右手邊係最後2個數字所構成的兩位數)

8x - 10 = 10x - 30 + x - 4
3x = 24
x = 8

所以小麗家中的電話號碼的第1個號碼是 8.
所以小麗家中的電話號碼 88887654.

自己計既,希望幫到你~

由於連續數可以係大至小又可以係小至大

即12345或54321

不妨「先」設

呢個數的第一個位係A
呢個數的第二個位係A
呢個數的第三個位係A
呢個數的第四個位係A
呢個數的第五個位係A+1
呢個數的第六個位係A+2
呢個數的第七個位係A+3
呢個數的第八個位係A+4

則 8A+10=10(A+3)+A+4

A = -8 唔掂...

不妨「再」設

呢個數的第一個位係A
呢個數的第二個位係A
呢個數的第三個位係A
呢個數的第四個位係A
呢個數的第五個位係A-1
呢個數的第六個位係A-2
呢個數的第七個位係A-3
呢個數的第八個位係A-4

則 8A-10=10(A-3)+A-4

A = 8

所以個號碼係 88887654

Let x be the first digit.
because the first 4 digit are the same, therefore it will become xxxx.
The last 5 digits will be (x+1)(x+2)(x+3)(x+4)or (x-1)(x-2)(x-3)(x-4), because they are exsecutive.So, It would be xxxx(x+1)(x+2)(x+3)(x+4) or xxxx(x-1)(x-2)(x-3)(x-4)
p.s. this time we can only guess what it is.
The other side will become 10(x+3)+(x+4) or 10(x-3)+(x-4) respectively.
This time we guess it is xxxx(x-1)(x-2)(x-3)(x-4)
The sum is x+x+x+x+(x-1)+(x-2)+(x-3)+(x-4)
And it will be 10(x-3)+(x-4) for the最後2個數字所構成的兩位數
x+x+x+x+(x-1)+(x-2)+(x-3)+(x-4)=10(x-3)+(x-4)
8x-10=11x-34
3x=24
x=8

we put in into the equation
LHS= 8+8+8+8+(8-1)+(8-2)+(8-3)+(8-4)= 54
RHS=10*(8-3)+8-4=54=LHS

Therefore, the telephone no is 88887654
I Hope I Can Help You!!!!!
And Happy New Year!!!!