determine the value of k in x^3+6x^2+kx+8=0 if 2 is a root (zero).?

2 ⤊

2007-12-29 06:07:11 · 3 answers · asked by metman208 2 in Science & Mathematics ➔ Mathematics

f(x) = x^3+6x^2+kx+8=0
f(2) = 2^3 + 6(2)^2 + 2k + 8 = 0
f(2) = 8 + 24 + 2k + 8 = 0
f(2) = 40 + 2k = 0
2k = -40
k = -20

2007-12-29 06:15:23 · answer #1 · answered by Anonymous · 0⤊ 0⤋

Well, just plug in x=2 and solve for k:

8 + 24 + 2k + 8 = 0
2k = -40
k = -20

2007-12-29 06:12:56 · answer #2 · answered by Pascal 7 · 2⤊ 0⤋

Youth. Pascal made algebra look simple.

2007-12-29 06:15:54 · answer #3 · answered by Anonymous · 0⤊ 0⤋