# math

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.

1. 👍 0
2. 👎 0
3. 👁 171

## Similar Questions

1. ### ALGEBRA 1!PLZ HELP!

Use the Substitution method to solve the system of equations. y - 2x = -5 3y - x = 5 Solve the first equation for y. y = 2x-5 Substitute that for y in the second equation and solve for x. Then use the value of x to substitute back

asked by SANDRO! on November 6, 2006
2. ### Precalculus

"Sketch the ellipse. Find the coordinates of its vertices and foci. 34. x^2 + 25y^2 - 6x - 100y + 84 = 0 (Hint: Complete the squares in x and y. Begin by writing the equation in this form: (x^2 - 6x + ___) + 25(y^2 - 4y + ___) =

asked by Emily on November 23, 2009
3. ### Algebra

I have some problems that I am having trouble with and I have some that need checking please. Thanks! Solve the equation. 4. (x+7/4)=2(x-1/6) Find all the value(s) of x that make thedenominator(s) zero. Then solve the equation. 6.

asked by Soly on August 21, 2007
4. ### 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? Hint using the values of a and b found in the equation, solve D = 0 for c. Consider

asked by toni on October 8, 2013
5. ### 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? Hint using the values of a and b found in the equation, solve D = 0 for c. Consider

asked by toni on October 8, 2013
6. ### math

The measures of two supplementary angles are in the ratio 5:1. What is the measure of the smaller triangle? A/B = 5 A + B = 180 Solve those 2 equations in two unknowns. B is the smaller angle. Hint: substitute 5B for A in the

asked by Peggy on February 23, 2007
7. ### Math

Solve the system by addition or substitution. 3x – 4y = 8 6x – 2y = 10 Please get me on the correct track for 3x -4y =8 x=4, y=1 for 6x - 2y =10 x= 2, y= 1 Solve one equation for x. 3x = 4y + 8 x = (4y + 8)/3 Insert that value

asked by Amanda on May 20, 2007
8. ### Math

Solve 2x-y+3z=8 x-6y-z=0 -6x+3y-9z=24 Did you notice that your third equation has the same normal as the third one? So visually I see two parallel planes intersected by third non-parallel plane, namely the second equation. So

asked by Lily on April 21, 2007
9. ### Substitution Method-Plz help

Use the Substitution method to solve the system of equations. x + y = -4 x - y = 2 solve for x in the second equation. x= y+2 Put that in for x in the first equation: x+y=-4 (y+2) + y = -4 solve for y. Then, x= y+2 i don't get

asked by Svetlana on October 17, 2006
10. ### Pre-Algebra

If the perimeter of a rectangle is 38 ft and the width is 9 ft, find its length. [Hint: The perimeter of a rectangle is given by P = 2L + 2W.] I don't know why this is a problem for you. P = 38 and W = 9. Solve for L. You have

asked by Tammy Evert on July 16, 2006
11. ### Algebra

To solve the system of equations, which expression could be substituted for x into the first equation? 3x-5y=14 x+4y=10 a)10-4y b)4y+10 c)(1/4)x+(5/2) d)(-1/4)x+(5/2) I have another problem just like this one so if you could

asked by maddie on July 27, 2007

More Similar Questions