Evaluate the expression b²-4ac given the following.

1. a=1 b=5 c=4
2. a=2 b=1 c=-21
3. a=4 b=4 c=1
4. a=1 b=-2 c=-2
5. a=9 b=0 c=16

Help me pleasseeee! thank you sa sasagot ❤