急 ! F4 Quadratic Equations 2

8.
y = [x - (√7 - 1)/2][x + (√7 + 1)/2]
y = x^2 + (√7 + 1 - √7 + 1)x/2 - (√7 -1)(√7+1)/4
y = x^2 + x - 3/2
9.
y = (x-0)(x-k)
y = x^2 - kx
10.
y = (x - m/2)(x+m)
y = x^2 + (m-m/2)x - m^2 /2
y = x^2 + mx/2 - m^2 /2
11.
y = [x - (2+√n)][x - (2-√n)]
y = x^2 + [-(2-√n)-(2+√n)]x + (2+√n)(2-√n)
y = x^2 - 4x + (4-n)
12a.
y^2 - 8y - 9 = 0
(y-9)(y+1) = 0
y = 9 or -1
b.
The new roots are 18 and -2.
(y-18)(y+2) = 0
y^2 - 16y - 36 = 0



2011-09-16 22:42:53 補充：
For # 8,9,10,11 , y = 0