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kow [346]
4 years ago
10

Solve x 2 - 4x - 7 = 0 by completing the square. What are the solutions?

Mathematics
1 answer:
Bingel [31]4 years ago
3 0

Answer:

x = 2±sqrt(11)

Step-by-step explanation:

x^2 -4x - 7 =0

Add 7 to each side

x^2 -4x -7+7 =0+7

x^2 -4x =7

To complete the square take the coefficient of the x term and  divide by 2 and then square it.  Add it to both sides

-4 /2 = -2 then square

(-2)^2 = 4

Add 4 to both sides

x^2 -4x+4 =7+4

x^2 -4x+4 = 11

Factor the left side into (x-b/2)^2

(x-2)^2 =11

Take the square root of each side

sqrt((x-2)^2) =±sqrt(11)

x-2 = ±sqrt(11)

Add to to each side

x-2+2 = 2±sqrt(11)

x = 2±sqrt(11)

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rosijanka [135]

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4 0
3 years ago
Read 2 more answers
According to the synthetic division below, which of the following statements are true? Check all that apply. -5(2 6 -8) -10 20 _
Sunny_sXe [5.5K]
***(2x²+6x-8):(x+5)=2x-4
     -2x²-10x
    ⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻
         -4x-8
          4x+20
    ⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻
              12 ⇒ A. statement is true.

***When x=-5⇒2*(-5)²+6*(-5)-8=12⇒B. statement is true.

***2x²+6x-8 can also be written as (x+5)*(2x-4)+12 so (x+5) is a factor of 2x²+6x-8⇒C. statement is true.

***When x=5⇒2*5²+6*5-8=72 is not 12⇒D. statement is not true

***
(2x²+6x-8):(x+5)=2x+16
     -2x²+10x
    ⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻
              16x-8
             -16x+80
        ⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻⁻
                     72⇒F. statement is not true

**
*E. statement is not true.





8 0
4 years ago
Read 2 more answers
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