F.2 maths

1. C=P (1+nr/100) IF C=60,P=40,n=5 ,FIND r .

(60)=(40) (1+(5)r/100)
60=(40) (1+r/20)
60=40+2r
2r= 60-40
r= 10

2.The size of each interior angle(A) of a regular polygon can be found by the formula A=(n-2x180。/n,where n is the number of sides of the polygon is 172。, find the number of sides of that polygon.

A=[(n-2)x180]/n
172=[(n-2)x180]/n
172n=(n-2)x180
172n=180n-360
18n=360
n=20

3. Simplify


X+Y Y-X
------ - ------
2X 2Y

=(X+Y)/2X - (Y-X)/2Y

=Y(X+Y)/2XY - X(Y-X)/2XY

=(YX+Y^2)/2XY - (XY-X^2)/2XY

=[(YX+Y^2) - (XY-X^2)]/2XY

=(Y^2 +X^2)/2XY


4. Simplify

c^2-d 3c-d
-------- + -------
d 3c

=(c^2-d)/d +(3c-d)/3c

=3c(c^2-d)/3cd +d(3c-d)/3cd

=(3c^3-3cd)/3cd +(3cd-d^2)/3cd

=[(3c^3-3cd)+(3cd-d^2)] /3cd

=(3c^3-d^2) /3cd

1. C=P (1+nr/100) IF C=60,P=40,n=5 ,FIND r .
即係 60 = 40 ( 1 + 5r/100 )
1. 60/40= 1 + 5r/100
2. 3/2 = 1 + r/20
3. 1.5 - 1 = r/20
4. 0.5 = r/20
5. 0.5 * 20 = r
final. 10 = r

1. r = 80
*唔知啱唔啱!!

2. 唔係好明這句:
where n is the number of sides of the polygon is 172。

3&4 唔知係咩!!
sorry@_@