Answer:
Step-by-step explanation:
We can use formula (a-b)² = a² -2ab + b².
In our example a = 3c^4 and b = 5c^6
40
Let the number be y
-1/2 × y = -20
y = -20 ÷ -1/2
y = 20 × 2
y = 40
B:14