## Monday, 11 March 2013

### Quadratic - Practice 6 (Ryan)

Practice 6, pg 156

1. Real and distinct means that discriminant > 0 not =0
Other than that the working is correct
It is clear and easy to follow as he states the values of a, b and c
Presentation is good as it clearly shows how he subs the values in

2. Neatness and organiztion: quite messy, took awhile to comprehend fully.
Mathematical concepts: Why did you assume D = 0? You should just state that D has to be more than zero to be real and distinct. Other that that answer is okay.
Explanation: Quite okay but should explain a bit more.

3. If the roots are real and distinct, the discriminant should be > 0, not equals to.
The explanation is not clear or vivid as D = 0 at first but was then > 0 in the end. The presentation is thus rather messy as workings are not clear and concepts contradict each other.

The presentation is sufficient.

4. Working is confusing because you introduce another variable a into the equation (in the line : a = a), so it might be unclear which "a" you are referring to

At the last 2 lines, you wrote -20a > 0, then the equation suddenly turned into a < 0. THe explanation is not clearly stated and is unclear. you should explain how you arrived at the ans a is less than 0 even though your previous statement stated that -20a is more than zero

Mathematical concept is prefectly fine and working is organised well.

5. The mathematical concept is incorrect. If the roots are real and distinct, the discriminant should be >0, and not D=0.
The workings are unclear and a little messy and not very easy to follow.
The answer answers to the question. However it is confusing as he stated that D=0, but ended off with D>0.

6. The organization is bad, a bit untidy and hard to follow.
The explanation is well written but could be elaborated slightly more.
A slight conception error. Real and distinct means discriminant must be more than 0 not equal to 0.
Nicely shown the substitution.