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Vika [28.1K]
2 years ago
15

What does k^2 -8k-20=0

Mathematics
2 answers:
Karolina [17]2 years ago
7 0
k^{2}-8k-20=0 \\ (k-10)(k+2)=0 \\  \\ k-10=0 \\ k=10 \\  \\ k+2=0 \\ k=-2 \\  \\ \boxed{k=-2\ and\ 10}
victus00 [196]2 years ago
3 0
K² - 8k - 20 = 0
k = <u>-(-8) +/- √((-8)² - 4(1)(-20))</u>
                       2(1)
k = <u>8 +/- √(64 + 80)</u>
                 2
k = <u>8 +/- √(144)
</u>              2<u>
</u>k = <u>8 +/- 12</u><u>
</u>            2
k = <u>8 + 12</u>          k = <u>8 - 12</u>
          2                        2
h = <u>20</u>                k = <u>-4</u>
       2                        2
x = 10                k = -2
<u />
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The mean of a data-set is the <u>sum of all observations divided by the number of observations</u>.

In this problem:

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Hence, the mean is:

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We want the mean to be of 0.9, thus:

M = 0.9

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4.2 + n = 0.9n + 4.5

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n = \frac{0.3}{0.1}

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3 more testes are need, each worth 5 points, hence, 15 more points are needed to bring up his average up to 90%.

A similar problem is given at brainly.com/question/25323941

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