quadratic eq.

1) ......log [ root(2x+2) / 4 ] = log [ 5/ root(3x+4) ]
...root( 6x^2 + 8x + 6x + 8 ) = 20
................6x^2 + 14x - 392 = 0
......................................x = [ - 14 +/- 98 ] / 12
......................................x = 7.......or ........-28/3
.
2a) y^2 - 3y + 2 = 0
...........(y-2)(y-1) = 0
.......................y = 2........or.......1
.
2b) 9^x - 3^(x+1) +2 = 0
....(3^x)^2 - 3 (3^2) + 2 = 0
.......3^x = 2 ............or ...............3^x = 1
...x log3 = log2................................x = 0
x = 0.631

2007-04-20 21:55:17 補充：
0.631 ---- 3s.f.0.63 ------ 2s.f.the "0" before the decimal point is not a sig. fig.

2)
(a) y^2-3y+2=0

(y-2)(y-1)=0

y=1 or 2



(b) Put y=3^x

y^2-3y+2= 0

(y-2)(y-1) = 0

y= 1 or 2

3^x = 1 or 2

3^x = 3^0

x = 0

[or]

3^x = 2

x log 3 = log 2

x = 0.63

x = 0 or 0.63

2007-04-21 21:50:49 補充：
Sorry 之前唔清楚你個sqt去到邊log(sq2x 2) - log4 = log5 - log(sq3x 4)log [(sq2x 2)/4] = log [5/(sq3x 4)](sq2x 2)/4 = 5/(sq3x 4)sq2x 2 = 20/(sq3x 4)2x 2 = 400/(3x 4) ← 大家都二次方佢(2x 2)(3x 4) = 4006x^2 8x - 386 = 0x = -8.72 or 7.382(b) x = 0 or 0.631