Question

if f(x) = x^3+Ax^2+Bx-3 and if f(1) = 4 and f(-1) = -6 what is the value of 2A+B?

Answer 1

f(1) = 1 + A + B - 3 = A + B -2 = 4
f(-1)= -1 + A -B -3 = A- B -4 = -6
A+B = 6
A-B = -2
2A = -4 A = -2
for A=-2, B = 8
2A + B = 2(-2) + 8 = 4

Answer 2

\[f(1)=1+A+B-3=4\]
so
\[A+B+6\]
\[f(-1)=-1+A-B-3=-6\] so
\[A-B=-2\]

Answer 3

solve
\[A+B=6\]
\[A-B=-2\] get
\[A=2\]
\[B=4\]

Answer 4

oh right, what jyouie said!

Answer 5

yours made more sense to me :P

Answer 6

oh I've did something wrong...sorry...I mistakenly saw it as -6 +2 sorry though