This is a way to factoring trinomials (there exist different equivalent methods).
Multiply the trinomial but the term accompanying . This is the second line. Then, you could take the square of the 
, ant try to create a factor () () that will correspond to the expression in the second line. That is, we want 
In ? we put the corresponding numbers that, if we multiply them we will obtain 42, and if we add them we will obtain 13. This numbers are 6 and 7. Then, we have 
The last step is divide by the number that we multipy in the first step.
Answer:
d
Step-by-step explanation:
The equation of the tangent line can be found using slope formula and fact that slope = dy/dx.
where (x0,y0) is point A ---> (0,-1)
Then rearrange equation into slope-intercept form:
Finally sub in x=0 into dy/dx to get slope at the point (0,-1)
