F.3 Maths Questions 40pts.

Q.1 Find the simplest quadratic equation (in the form of Ax^2+bx+c= 0) with
roots 1 and 2.
When the roots can be 1 and 2, we get x=1 and x=2
x-1=0, x-2=0
(x-1)(x-2)=0
x^2-3x+2=0 is the simpiest form of the quadratic equation of the roots 1 and 2.

Q.2 Factorize the following parts:
2y^2-y^2+8y-4
= y^2 + 8y - 4
= y(y+8) - 4 ??? or y^2 +4(2y-1) ???? or = y(y+4)+4(y-1)????????

Q.3 三角形的底減少20%, but area no change, find the height increase ? %?
Let b cm be the base, h cm be the height, and A cm^2 be the area, and x% be the percentage increase..
(1-20%)b * (1+x%)h = a
0.8bh(1+x%)=a
0.8a(1+x%)=a
1+x%=1/0.8
x%=0.25
x=25
Hence, the height increases 25%...

2009-12-27 20:39:03 補充：
Q.2唔係好識~~~不過都希望幫到你啦~~~

2009-12-27 20:53:03 補充：
那麼 6y呢?

2009-12-27 21:03:00 補充：
Q.2 Factorize the following parts:
2y^2-y^2+8y-4
= y^2 + 8y + 16 -20
= (y+4)^2 - 20 ????一定有剩= =
此式最小的可能為-20

q2
2y^2-4-y^2+8y
=2(y-2)-y^2+2y+6y
=2(y-2)-y(y-2)+6y
=(y-2)(2-y)+6y