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# Discriminant question watch

1. I have been given this question from Core 1, and am stuck on it. Any help would be very useful and appreciated.

Given that the equation x² - 3bx + (4b+1) = 0 has a repeated root, find the possible values of the constant b.

I have got as far as using the discriminant b²-4ac = 0
and putting in the values

-3b² - 4 x 1 x (4b +1) = 0
-3b² - 16b - 4 = 0
Where do i go from here?
2. you've done it wrong, you should write:

(-3b)^2 - 4*1*(4b+1) = 0
9b^2 - 16b - 4 = 0
(9b+2)(b-2) = 0

b = 2, or b = -2/9
3. thanks very much

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Updated: January 29, 2006
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