Posted by Zach on Sunday, November 15, 2009 at 9:30pm.
Write a quartic function that has roots that are 3+5i, -4 and 7 and
I have tried it a bunch of times and can't seem to get it.
I multiplied them together
I was a little unsure what f(-3)=53 means.
I thought I should plug -3 in for x and it should equal 53. That doesn't work.
Can you please help me see where I went wrong?
- Pre Calc - Reiny, Sunday, November 15, 2009 at 10:12pm
Ahh, how would you know that the function wasn't
f(x) = a(x-3+5i)(x-3-5i)(x+4)(x-7)
Wouldn't it still have those same roots if you set f(x) = 0 ?
I am going to trust that you expanded correctly.
Now let f(-3) = 53
53 = a((-3)^4 - 9(-3)^3 + 24(-3)^2 + 66(-3) - 952)
solve for a, then multiply your expanded expression by that value.
- Pre Calc (please explain) - Bob Dylan, Sunday, November 15, 2009 at 10:23pm
How do you know that it is supposed to have an a in front?
- Pre Calc - Zach, Sunday, November 15, 2009 at 10:47pm
I get where a comes from. Is the answer 53/-610? It doesn't seem right.
- Zack Pre Calc - Reiny, Sunday, November 15, 2009 at 10:56pm
I got -53/610 also
- Bob Dylan - Pre Calc - Reiny, Sunday, November 15, 2009 at 10:59pm
" How do you know that it is supposed to have an a in front? "
Bob, I guess the answer was blowing in the wind.
Answer this Question
- Pre-Calculus - Hello, I have tried solving this using the rational roots theorem...
- Pre Calc (For Reiny) - Thanks so much your method worked perfectly! My solution ...
- Pre-Calculus - Graphing Polynomials Decide whether each of the following is ...
- Pre-Calc - I am having a great deal of difficulty with this problem. An open box...
- pre calc - Find an equation of the cubic polynomial f(x) = ax3 + bx2 + cx + d ...
- Pre-Calc/Trig - Use Descartes' rule of signs to describe the roots of the ...
- Pre-trig/Calc - Please help me. Use Descartes' rule of signs to describe the ...
- Pre-Calculus/Trig Check please and help - Could someone please check the first ...
- pre calc - (-9x^3-6x^2-x+3)/(2x^2+5x+2) I have figured out the equation for the ...
- Pre-Calc/Trig... - Helpp needed, this is sort of confusing me. Describe the ...