Solve by completing the square. x2 - 4x – 20 = 0

A. x = {-2±6√2}

B. x = {2+6√2}

C. x = {2+2√6}

D. x = {-2±2√6}

Show your work.​

Step-by-step explanation:

Subtract

20

from both sides of the equation.

x

2

−

4

x

=

−

20

To create a trinomial square on the left side of the equation, find a value that is equal to the square of half of

b

.

(

b

2

)

2

=

(

−

2

)

2

Add the term to each side of the equation.

x

2

−

4

x

+

(

−

2

)

2

=

−

20

+

(

−

2

)

2

Simplify the equation.

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x

2

−

4

x

+

4

=

−

16

Factor the perfect trinomial square into

(

x

−

2

)

2

.

(

x

−

2

)

2

=

−

16

Solve the equation for

x

.

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x

=

2

±

4

i

x= -3 and

step-by-step explanation:

to find the roots of a cubic, use division or factoring to find the factors then set equal to 0. as this is a difference of cubes, it factors into

where a is the cube root of .

here   this is 27 and the cube root of 27 is 3. so we write using the form:

.

set each factor to 0 and solve for x.

x-3=0

x=3

the quadratic expression does not factor and must be solved using the quadratic formula.

where a = 1, b=3, and c=9

this cubic has two complex roots.

can you put the picture up?

step-by-step explanation: