f(x)=ax^2+bx+c

[shawie]

hi... i am in precalculus and i am having a VERY hard time with this class. If someone can help me figure out my notes PLEASE help me!

Instructions: Use Given Values to find equation of the form f(x)=ax^2+bx+c

f(0)=5
f(1)=10
f(2)=19

.....

 

[Guest]

f(x)=ax^2+bx+c

f(0)=5
f(1)=10
f(2)=19


The f(0) =5 means sub the value x=0 into the equation and the result is equal to 5. Doing this for each of the values will produce 3 equations with 3 unknowns which is then able to be solved.

f(0) = a(0)^2 + b(0) + c
5 = c because f(0) = 5 from above

keep going and it is solved.

 

[Guest]

With your notes----
I would assume the -2 referes to equation 2 from above not a calculation statement of minus 2

 

[shawie]

With your notes----
I would assume the -2 referes to equation 2 from above not a calculation statement of minus 2

i'm sorry i did not understand that.

 

[Guest]

sorry for the typo...
using f(0) you found c=5...use this in the following equations
ok , in your notes you have the following layout.
2) a + b +5 = 10.......this comes from the step of placing x= 1 into the equation you were given, and the answer is equal to 10

3) 4a + 2b + 5 =19.....this comes from placing x= 2 into the equation and the answer is equal to 19

(a+b=5) -2

If you rewrite equation 2 from above you get
a+b =10-5
a+b = 5......which comes from equation 2

The -2 is refering to this .
Is this better?

 

[shawie]

yes! thank you!!