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Andreyy89
3 years ago
11

Factor by completing the square 5x^2-21=10x

Mathematics
1 answer:
velikii [3]3 years ago
4 0
Solve for x over the real numbers:
5 x^2 - 21 = 10 x

Subtract 10 x from both sides:
5 x^2 - 10 x - 21 = 0

Divide both sides by 5:
x^2 - 2 x - 21/5 = 0

Add 21/5 to both sides:
x^2 - 2 x = 21/5

Add 1 to both sides:
x^2 - 2 x + 1 = 26/5

Write the left hand side as a square:
(x - 1)^2 = 26/5

Take the square root of both sides:
x - 1 = sqrt(26/5) or x - 1 = -sqrt(26/5)

Add 1 to both sides:
x = 1 + sqrt(26/5) or x - 1 = -sqrt(26/5)

Add 1 to both sides:
Answer:  x = 1 + sqrt(26/5) or x = 1 - sqrt(26/5)
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How to solve these two problems ?
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8)  \theta is -0.896 radians

9) length of arc is 41.91 cm

Solution:

8)

Given that,

tan\ \theta = \frac{-5}{4}

\theta is in quadrant 4

To find: \theta

From given,

tan\ \theta = \frac{-5}{4}\\\\\theta = tan^{-1} \frac{-5}{4}\\\\\theta = tan^{-1} (-1.25)\\\\\theta = -51.34

Thus value of \theta is -51.34 degrees

Convert degrees to radians

-51.34\ degree = -51.34 \times \frac{ \pi }{180}\ radian\\\\-51.34\ degree = -0.896\ radian

Thus \theta is -0.896 radians

9)

From given,

radius = 15.4 cm

\theta = \frac{13 \pi }{15}

<em><u>The length of arc when angle in radians is:</u></em>

arc\ length = r \times \theta\\\\arc\ length = 15.4 \times \frac{ 13 \pi }{15}\\\\arc\ length = 15.4 \times 2.721\\\\arc\ length = 41.91

Thus length of arc is 41.91 cm

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7

Step-by-step explanation:

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