Question

Could someone verify if I got two answers to two problems right?

f(x)=x^2-9x+15 find x and y intercepts
-9+square root of 21/2,0
-9-square root of 21/2,0

x^2-x+3=0 solve and find x-intercepts
(1+square root of -11/2,0)
(-1-square root of -11/2,0)

Answer 1

for ax^2 + bx + c = 0,
x = (-b ± √(b^2 - 4ac) )/(2a)

so for yours, for the x-intercepts
x = (+9 ± √(81-4(1)(15))/2
= (9 ± √21)/2

for the y-intercept, let x=0
f(0) = 0-9+15 = 15

for the second:
x-intercept: (1 + √-11)/2 , (you had 1 + √-11/2 ---> only the last term was divided by 2 )
y-intercept : 3

Answer 2

Hi
I don't understand how you are getting the y intercept. I am so confused about which numbers are solutions, vertex, x-intercepts, y-intercepts etc.

Can you write out an example of an equation and how you get each number from a formula. I have been in this class for nine weeks and with all the information I have at my disposal I still am confused.