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Determine the possible zeros or roots of the given polynomial functions using the Rational Root Theorem. Show your solution.

1.) f(x) = x3 - 4x² - 19x - 14
2.) f(x) = 4x³ - 4x² 21x - 9​


Sagot :

Answer:

1. (x+1) (x-7) (x+2) = 0 true.

x= -1 , 7 , -2

Step-by-step explanation:

1. f(x)= - 4x² - 19x - 14

Set x³ - 4x² - 19x - 14 is equal to 0.

- 4x² - 19x - 14 = 0

Solve for x:

Factor the left side of the equation.

Factor x³ - 4x² - 19x - 14 using the rational roots test.

If a polynomial function has integer coefficients, then every rational zero will have the form

p/q where p is a factor of the constant and q

where p is a factor of the constant and q is a factor of the leading coefficient.

p= ±1 , ±14 , ±2 , ±7

q= ±1

Find every combination of ± p/q . These are the possible roots of the polynomial function.

±1 , ±14 , ±2 , ±7

Substitute the -1 and simplify the expression In this case, the expression is equal to 0 so -1 is a root of the polynomial.

Substitute −1 into the polynomial. (−1)³ −4 (−1)² −19 . −1 −14

Raise -1 to the power of 3.

-1 -4 (-1)² -19. -1 -14

Raise -1 to the power of 2.

-1 -4 - 1 -19. -1 -14

Multiply -4 by 1

-1 -4 -19. -1 -14

Subtract 4 from -1.

-5 -19. -1 -14

Multiply -19 by 1.

-5 + 19 - 14

Add -5 and 19.

14 - 14

Subtract 14 from 14.

0

Since -1 is a known root, divide polynomial by

x+1 to find the quotient polynomial. This polynomial can then be used to find the remaining roots.

4x²19x14

x+1

Divide -4x² - 19x - 14 by x+1.

-5x -14

Write - 4x² -19x - 14 as a set of factors.

(x+1) (-5x-14) = 0

Factor -5x-14 using the AC method.

Consider the form of +bx+c . Find a pair of integers whose product is c and whose sum is b. In this case whose product is -14 and whose sum is -5,-7,2.

Write the factored form using these integers.

(x+1) ((x-7) (x+2))=0

Remove unnecessary parenthesis.

(x+1)(x-7)(x+2)=0

If any individual factor on the left side of the equation is equal to 0, the entire expression will be equal to 0.

x+1=0

x-7=0

x+2=0

Set the first factor equal to 0 and solve.

x=-1

Set the next factor equal to 0 and solve.

x-7=0

Add 7 to both sides of the equation.

x=7

Set the next factor equal to 0 and solve.

x+2=0

Subtract 2 from both sides of the equation.

x=2

The final solution is all the values that make (x+1)(x−7)(x+2)=0 true.

x=−1,7,−2