Some mixed questions I need some confirmation on.

1:

Find (a) the directrix, (b) the focus and (c) the roots of the parabola $\displaystyle y=x^2-5x+4$.

I can find the directrix and the focus no problem, but i do not understand what they mean by "roots". Do they mean the roots(positive and negative) of the equation or something else?

"roots" are the solutions to
2:

Write the first three terms of the expansion of $\displaystyle (a-b)^{10}$.

Answer:

$\displaystyle a^{10}+10a^9b-45a^8b^2$

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3:

What are the last three terms of $\displaystyle (a-b)^7$?

Answer:

$\displaystyle 21a^2b^5+7ab^6-b^7$

one sign error
Thank you!