dang_thitham
Find f(-2) if f(x) = 2x2 + kx + 2 and f(1) = 3.
Delete
Share
This Question is Closed
dang_thitham
Best Response
You've already chosen the best response.
1
need help
anonymous
Best Response
You've already chosen the best response.
0
replace x by 1 and solve
\[f(1)=2+k+2=3\] for k
dang_thitham
Best Response
You've already chosen the best response.
1
k=-1?
dang_thitham
Best Response
You've already chosen the best response.
1
no it is wrong
abtrehearn
Best Response
You've already chosen the best response.
0
We find what k is by plugging 1nfor x into the original function and setting the result equal to 3:
2*1^2 + k*1 + 2 = 3, so k = -1, and the function is\[f(x) = 2x^{2} - x + 2.\]We evaluate this function at x = -2:
f(-2) = 8.
dang_thitham
Best Response
You've already chosen the best response.
1
so what is its' result?
abtrehearn
Best Response
You've already chosen the best response.
0
I glitched. f(-2) = 12.
dang_thitham
Best Response
You've already chosen the best response.
1
why?
abtrehearn
Best Response
You've already chosen the best response.
0
Did you get k = -1?
dang_thitham
Best Response
You've already chosen the best response.
1
yes
anonymous
Best Response
You've already chosen the best response.
0
looks like if you solve larger less than twice the smaller. make x the larger then we get
\[2+k+2=3\] you get
\[k=-1\] yes? so now you have
\[f(x)=2x^2-x+2\] and if you want
\[f(-2)\] you compute
\[f(-2)=2(-2)^2-(-2)+2\]
dang_thitham
Best Response
You've already chosen the best response.
1
oh ok
abtrehearn
Best Response
You've already chosen the best response.
0
You use the information to find the value of f(-2).
dang_thitham
Best Response
You've already chosen the best response.
1
ok I understand now.Thanks
abtrehearn
Best Response
You've already chosen the best response.
0
:^)