Please help me with this im so co fused

In triangle abc, the length of side ab is 12 cm, the length of side bc is 5 cm, and the length of side ca is 9 cm. find the measure of angle a using the law of cosines.

Rewrite the following quadratic functions in intercept or factored form. show your work. y = 5x^2 + 10x

Which is an x-intercept of the graphed function? (0, 4) (–1, 0) (4, 0) (0, –1)