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Hashem (Student) May 29 2015
Usually the easiest way to find the root of a quadratic is to factorise it so you have something a form similar to - (x+2)(x-1)=0.
From here you need to find a value for x that makes each bracket equal to zero. Here we can see our answers are x = 1 and x = -2.
If the equation cannot be factorised our backup method that is slightly more complicated but always correct is to use the quadratic equation.
This is given as x = (-b ± (b2-4ac)1/2)/2a,
Where a, b and c come from your original quadratic as ax2+bx+c.see more
In general the preterite is used when something has been completed. If an action has a definite start and end then you should be using the preterite, this can be both if it is something that happened once or if it is something that was repeated a specific number of times.
For example - Ayer, fue al cine. (Yesterday, he went to the cinema)
Me llamó dos veces. (He called me twice)
The imperfect is used when you don't have a definite end point. This could be something that happened generally in the past or something that has not yet been completed. It is also used often as a way of setting up the use of another past tense.
For example - Cuando era niño, tuve un fútbol. (When I was a child, I had a football)
Yo estaba hablando cuando tosía. (I was talking when he coughed)see more