Answer:
Part A
We need to determine values of x for which 2x−1 is positive
⇒ 2x - 1 > 0
⇒ 2x > 1
⇒ x >
Hence, for all values of x that are greater than , the binomial 2x-1 is positive
Part B
We need to determine values of y for which 21−37 is negative
⇒ 21-3y < 0
⇒ 21 < 3y
⇒ 7 < y
Hence, for all values of y that are greater than 7, the binomial 21-37 is negative
Part C
We need to determine values of c for which 5−3c is greater than 80
⇒ 5-3c > 80
⇒ -3c > 75
⇒ -c > 25
⇒ c < -25
Hence, for all values of c that are less than -25, the binomial 5-3c is greater than 80