f2 數學 math 6題...十分

1)
26km = 2,600,000cm
therefore, 4cm on a map = 2,600,000 cm
2,600,000 / 4 = 650,000
Therefore, the scale of the map is 1:650,000

2)
(3x-y)(2y-5x)
=2y((3x-y)-5x(3x-y)
=6xy-2y(y)-15x(x)+5xy
=11xy-2y(y)-15x(x)
[y(y) = y to the power of two(y的二次方), [x(x) = x to the power of two(x的二次方).]

3)
28800*5.5%*3+28800
=4752+28800
=$33552

4)
130*(1-30%)
=130*70%
=$91

5)
If x=-2, y=5,
R.H.S.=3x+8y
=3(-2)+8(5)
=-6+40
=34
=L.H.S.
Therefore the point lines on the straight line.
[R.H.S. = Right Hand Side, L.H.S. = Left Hand Side.]

6)
The sum of the all the external angles = 360 degree.
All the interior angles should be equal for regular polygon.
The number of angles = 360 / (180-175.5)
=80
Since number of angles = number of sides,
Therefore, there are 80 sides.

2008-09-05 21:18:20 補充：
Sorry for 3),
the answer is only asking for the interest.
Therefore, the answer should be $4752.
The one I wrote is included capital( the sum you put in).

1) 1 : 6.5
2 2
2) 11xy-2y -15x

3) $4752

4) $91

5)Yes
3x+8y=34
(3)(-2)+(8)(5)=34
34=34

6)80

1) 4cm:26km
=4:2 600 000
=1:650 000

2) (3x-y)(2y-5x)
=6xy-15x(x)-2y(y)-5xy
=-15x(x)-2y(y)+xy ps. x(x)/y(y) is mean x/y square

3) simple interest=$(28800*5.5%*3)
=$4752

4) selling price=$130*(1-30%)
=$91

5) if x=-2 and y=5,
LHS=3x+8y
=3(-2)+8(5)
=34
since LHS=RHS
so point(-2,5) lines on the straight line graph that represents the equation 3X+8y=34

6) Let n be number of sides of the regular polygon
[(n-2)*180]"除"n=175.5
(180n-360)"除"n=175.5
180n-360=175.5n
4.5n=360
n=80
so number of sides of the regular polygon is 80

2008-09-05 20:33:57 補充：
2) (3x-y)(2y-5x)
=6xy-15x(x)-2y(y)+5xy
=-15x(x)-2y(y)+11xy <------計錯左係+11xy

ps. x(x)/y(y) is mean x/y square