Answer:
a) The student cannot receive an A in the class.
b) The student must score 119 in the third exams to make an A. This is clearly not possible, since he cannot make 119 in a 100-points exam.
c) The student can make a B but he must score at least 84 in the third exam.
Step-by-step explanation:
To make an A, the student must score 315 (350 x 90%) in both home and the three exams.
The student who scored 35 (7 + 8 + 7 + 5 + 8) in the homework and 161 (81 + 80), getting a total of 196, is short by 119 (315 - 196) scores in making an A.
To make a B, the student must score 280 (350 x 80%) or higher but not reaching 315.
B ≥ 280 and < 315.
Since, the student had scored 196, he needs to score 84 and above to make a B in the last exam.
Remember that i²=-1
the conjugate of a+bi is a-bi
so
3-4i
the conjugate is 3+4i
product
(3-4i)(3+4i)
hey, this looks familiar
remember (a-b)(a+b)=a²-b²
so
(3-4i)(3+4i)=(3)²-(4i)²=9-(16i²)=9-16(-1)=9+16=25
the product is 25
it's conjugate is 3+4i