math

posted by .

solve the equation x^3-5x^2-4x+20=0

I need a hint on how to solve this

Look for the first root by graphical means or trial-and-error. Note that when x=2,
x^3-5x^2-4x+20 = 8-20 -8 +20 = 0.
Therefore 2 is one root and x-2 is a factor.
Next, divide x-2 into x^3-5x^2-4x+20 using long division, to get a quadratic factor. The result is
(x-2)(x^2-3x-10)
The quadratic factor is just (x-5)(x+2), so the equation becomes
(x-2)(x+2)(x-5) = 0
This tells you that the other roots are x = -2 and +5.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. help!

    A horizontal translation is applied to the graph of y= X^ 3 + 2 so that it will pass through (3, 10) what is the new equation for the graph?
  2. algebra

    solve 4^3x-4=32^x+2 Please help! Do you mean 4^(3x) -4 = 32^x +2 ?
  3. need help in math,

    Translate to a system of equations and solve using the addition method. The sum of two numbers is88. The difference is 22.Find the numbers?
  4. math

    Still looking at how to solve these... Both are cubic polynomials?
  5. logarithmic eq:

    3logx = 6-2x Thanks This is a problem that is best solved by iteration, or graphing. I recommend graphing. There is no closed-form solution. You need to solve it by graphical or iteration (trial and error) methods. The answer is approximately …
  6. Math

    I can't for the life of me solve this! 6x^2-23x+15=0 6x^2-23x+15 = (a x + b) (c x + d) --> a c = 6 (1) a d + b c = -23 (2) b d = 15 (3) You could write down all possibilities for a and c (Eq. 1) and all possibilites for b and d …
  7. algebra

    solve for x (24+2x)(10+2x) - 240 = 152 First multiply. 24(10) = ___ 2x (2x) = ____ Now subtract 240. Can you finish the problem from here?
  8. Pre Algebra

    Please help me with some problems. Thank you! Solve the equation by square root property. 3. 2x^2 = 26 I don't understand how to solve this problem. Solve the equation using the quadratic formula. 7. 7x^2=-8x -2 This is what I got …
  9. algebra

    Im lost i don't know how to do this can someone show me step by step how to solve this For what value does c does the equation have one real root?
  10. algebra

    Im lost i don't know how to do this can someone show me step by step how to solve this For what value of c does the equation have one real root?

More Similar Questions