
now, a line perpendicular to that one, will have a "negative reciprocal" slope, thus
Answer:
Option B. 
Step-by-step explanation:
we know that
The formula to solve a quadratic equation of the form
is equal to
in this problem we have

so
substitute in the formula
Remember that

substitute

Answer: perceived lack of anonymity
Step-by-step explanation:
The source of bias that occurs when a group of students are asked to evaluate their teacher mid-quarter is a perceived lack of anonymity.
Perceived lack of anonymity occurs when the responder is afraid that if he or she gives an honest answer, it can end up affecting them negatively.
In this case, the students may be afraid that giving an honest opinion on the teacher will affect them.