Question

The curve y=ax^2+bx+c passes through points (1,8) (0,5) and (3,20) Find the values of a, b and c.

Answer 1

start by plugging in (0,5) and see what you get

Answer 2

5=c

Answer 3

really good

Answer 4

now plug in (1,8) using c=5 and see what you get

Answer 5

8=a+b+5

Answer 6

or 3=a+b
now plug in (3,20) using c=5 and see what you get

Answer 7

20=9a+3b+5

Answer 8

or 15=9a+3b

Now, you have two simultaneous linear eqs that you can solve by substitution or elimination to come up with a and b and you have then answered the question

Answer 9

brilliant.

Answer 10

how did you know how to solve this?

Answer 11

I did not. I have been studying math for many years and always try to plug in a zero to see what happens. In this case it led me to find c and then since I had 2 other points, I started to see where it would lead.