中4MATSH A0A好易 xxxx Q 13,14,15

[Set 1]
1.
Since the equation has two unequal real roots, the discriminant of the quadratic equation > 0.

(6)^2 - 4(k)(3) >0
36 - 12k > 0
-12k > - 36
k < 3 (Pay attention to the change in inequality sign)

2.
I can't find the question.

[Set 2]
1.
I can't find the question.

2.
(b)
0 = log (10k) - 2
log (10k) = 2
log (10k) = log (100)
10k = 100
k = 10

[Set 3]
1.
(a)
log12 + log15 - log18
= log (12x15/18)
= log 10
= 1
(b)
(log20 - log5)/log16
=[log(20/5)]/log16
=log4/(2log4)
=1/2

2.
(a)
log(27/45)
=log(3/5)
=log3 - log5
=x-y
(b)
log250-log90
=log(250/90)
=log(25/9)
=log25 - log9
=2log5 - 2log3
=2y -2x

[Set 4]
(a)
5.5=-log(x)
log(x) = -5.5
x = 10^(-5.5)
x = 3.2x10^(-6) (2 sig. fig.)
Therefore, the concentration of hydrgen ions in a shampoo that has pH of 5.5 is 3.2x10^(-6) mod/dm^3

2.
[log(x-12) - log4]/log25 = 1/2
2[log(x-12) - log4] = log 25
log(x-12) - log4 = log 5
log [(x-12)/4] = log 5
(x-12)/4 = 5
x-12 = 20
x = 32

If there is a mistake, please inform me.

2007-12-06 00:15:18 補充：
補充上面:[Set 1]2.我找到你的問題出處了.(a)Length of the frame = (30 + 2x) cmWidth of the frame = (20 + 2x) cm(b)(30+2x)(20+2x) - (30)(20) = 1594x^2 + 100x + 600 - 600 = 1594x^2 + 100x - 159 = 0(2x-3)(2x+53) = 0x = 3/2 or x = -53/2 (rejected)