Need help! When f(x) = -12, Solve the equation: x³ - 3x² - 4x?

Answer 1

You made a mistake copying a question. You want us to solve an equation but you don't tell us what equation you want us to help you with. x^3-3x^2-4x is not an equation. Equation is a statement with = sign.
Unless this is what you meant:
if f(x)=-12 solve x^3-3x^2-4x=f(x)
If this is a case then:
x^3-3x^2-4x=-12
x^3-3x^2-4x+12=0
x^2(x-3)-4(x-3)=0
(x^2-4)(x-3)=0
(x-2)(x+2)(x-3)=0
x-2=0; x+2=0; x-3=0 - multiplication is equal to zero if one term is zero.
x=2 or x=-2 or x=3

Answer 2

Don't listen to the last answers they are wrong

assuming f(x) = x^3-3x^2-4x

then you have -12 = x^3-3x^2-4x


TO solve it you need to make it equal to zero

so x^3-3x^2-4x+12 = 0

Then you have to find the factors of the cubic and solve it for x

Answer 3

2 - x²)^(1/2) = x(2 - x)

2 - x² = x²(2 - x)² = x²(4 - 4x + x²) = 4x² - 4x³ + x^4

0 = x^4 - 4x³ + 5x² - 2
x^4 - 4x³ + 5x² - 2 = 0

(x - 1)(x³ - 3x² + 2x + 2) = 0

This has two real solutions.
x = 1

Answer 4

When f(x) = -12, Solve the equation: x³ - 3x² - 4x?

(-12)³ - 3(-12)² - 4(-12)
-1728 -3(144)+48
-1728 -432 + 48
-2160 + 48
-2112

Answer 5

Bring x out:
x (x^2 - 3x -4)
Sub x = -12 into above line...derive the below:
= -12 [ (-12)^2 - 3*(-12) - 4]
= -12 [144 - (-36) - 4]
= -12 [144 + 36 - 4]
= -12 * [176]
= -2112

Answer 6

Substitute x= -12 in the equation

(-12)^3-3*(-12)^2-4*(-12)

-1728-432-48

do the math

Answer 7

f(x)=x³ - 3x² - 4x
f(x)=-12

=>
x³ - 3x² - 4x=-12
x³ - 3x² - 4x=-12
x(x² - 3x-4)=-12
x(x+1)(x-4)=-12
try iteration
x=1..
1(1+1)(1-4)=-6
LHS not equal to RHS
next
x=2
2(2+1)(2-4)=12
LHS=RHS

So answer is
x=2

Got it?

Answer 8

x^3-3x^2-4x=-12
x^3-3x^2-4x+12=0 (add 12 from both sides)
Factor by grouping:
x^2(x-3)-4(x-3)=0
(x^2-4)(x-3)=0
(x+2)(x-2)(x-3)=0
x=-2, 2, 3

Answer 9

plug (- 12) in for all x's.

(-12)^3 - 3(-12)^2 - 4(-12)

(-1728) - 3(144) - 4(-12)

(-1728) - (432) - (-48)

-1728 - 432 + 48

- 2160 + 48

- 2112

Answer 10

f(x) = x³ - 3x² - 4x

x = - 12

f( - 12) = (- 12)³ - 3(- 12)² - 4(- 12)

f(- 12) = - 1728 - 3(144) - ( - 48)

f(- 12) = - 1728 - 432 + 48

f( - 12) = - 2160 + 48

f( - 12) = - 2112

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