English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
All categories

Find all of the zeros of the following function.

p(x)=6x^4+22x^3+11x^2-38x-40


I'm having all sorts of problems figuring this one out. Can someone walk me through it step-by-step? Thanks.

2007-02-01 14:44:48 · 5 answers · asked by Anonymous in Science & Mathematics Mathematics

5 answers

You need to look at factors of 6 and 40 to find potential solutions. Any rational solutions will be a factor of 40 divided by a factor of 6 (positive or negative). Synthetic division is your best bet, but due to the difficulty of aligning it here I won't write it out.

Testing a few possibilities, we find x = -2 is a zero:
p(2) = 6(16) + 22(-8) + 11(4) - 38(-2) - 40 = 96 - 176 + 44 + 76 - 40 = 0. So divide through by (x+2) to get
p(x) = (x+2)(6x^3 + 10x^2 - 9x - 20)

Let q(x) = 6x^3 + 10x^2 - 9x - 20. Now we need factors of 20 divided by factors of 6.
We find x = 4/3 is a solution: q(4/3) = 6(64/27) + 10(16/9) - 9(4/3) - 20 = (384 + 480 - 324 - 540)/27 = 0. So we get
q(x) = (3x - 4) (2x^2 + 6x + 5)
The discriminant of this quadratic is 6^2 - 4(2)(5) = 36 - 40 = -4 < 0, so there are no additional zeros.

So the only zeros of p(x) are -2 and 4/3.

2007-02-01 15:08:07 · answer #1 · answered by Scarlet Manuka 7 · 0 1

EWWWW people like you should be put into an institution and put through shock therapy to keep your two sense to yourself when no one asked you opinion. This is from the question pregnancy cravings! How was this your place? You need some manners!!! I have no problems with how other people live their life that is there business not yours. You can only defend yourself when you are in front of the creator you my friend are not the creator so do not judge others only yourself, CHICK

2007-02-04 20:33:30 · answer #2 · answered by Katie 3 · 0 0

try to group; suppose: (2x^2+ax+b) (3x^2+cx+d) = 6x^4 +(3a+2c)x^3 +(3b+2d+ac)x^2 +(cb+ad)x +bd; also suppose a, b, c, d are integer;
hence 3a+2c=22; 3b+2d+ac=11; cb+ad=-38; bd=-40;
♠ now 3a+2c=22, hence a must be even, b must be odd, c must be even, d must be even; and b or d must be negative;
♣ so 3(a/2)+c =11, then 3+8=11 and {a=2, c=8} or 9+2=11 and {a=6, c=2};
♦ now 3b+2d+ac=11, hence 3b +4(d/2) +5=0 or 3b +4(d/2) +1=0; thus 3b+1 must be divisible by 4; thus (3b+1)/4 +1 =-d/2 or (3b+1)/4 =-d/2, multiply by b,
♥ b(3b+1)/4 +b=20 or b(3b+1)/4 =20; b(3b+1)/4 +b=20 is non-consistent,
thus b=5 and d=-8; since(♦) 3b+2d+ac=11, then ac=12, so(♣) a=6 and c=2;
check: (2x^2+6x+5) (3x^2+2x-8) =6xxxx +(18+4)xxx +(15+12-16)xx +(10-48)x –40 OK!
☻2x^2+6x+5=0, no real roots!
☺3x^2+2x-8=0, x1=-2, x2=4/3;

2007-02-02 01:49:43 · answer #3 · answered by Anonymous · 0 1

was gona answer but someone alrdy did that so lol just saying i read your comment to the racist asians lol ching chong funny ****

2007-02-02 01:16:28 · answer #4 · answered by Martin SCholserZ 3 · 0 1

Gosh. I like math and this is a tough one...... Let me think on this a bit.

2007-02-01 22:53:45 · answer #5 · answered by nicewknd 5 · 0 1

fedest.com, questions and answers