PLEASSSE 有無人可以教我計呢幾條數? f2 level

2007-07-18 4:34 am

1) factorize (x-y)^2 -1 ps ^2 = square
2) factorize x^2-x(y-1) ps ^s = square
3) 2 cos(2A +10)= sin30 find the value of A
4) if a =2b=3c, find the ratio of a to b to c
5) find the value of x and y if 2x+3y=3x-2y+7=12

吳該牙盡做 pleasee
我真係一頭無緒

回答 (1)

用戶4872

2007-07-18 5:28 am

✔ 最佳答案

1) factorize (x-y)^2 -1
= (x-y)^2 - (1^2)
= (x-y-1)(x-y+1)
as A^2 - B^2 = (A-B)(A+B)

2) factorize x^2-x(y-1)
= x[x-(y-1)]
= x(x-y+1)

3) 2 cos(2A +10) = sin30
2 cos(2A +10) = 1/2
cos(2A +10) = 1/4
(2A +10) = 75.52 or 284.48
A = 32.76 or 137.24 (degree)

4) if a =2b=3c
a/b = 2/1
b/c = 3/2
a/c = 3/1 = 6/2
hence a:b:c = 6:3:2

5)
2x+3y = 12 -- (i)
3x-2y+7= 12 -- (ii)
3*(i) - 2*(ii),
6x + 9y - (6x - 4y + 14) = 36 - 24
13y - 14 = 12
y = 26/13 = 2
sub y = 2 into (i)
2x + 3(2) = 12
2x = 6
x = 3
therefore, x = 3 & y = 2

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