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User Chrysoula
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2 Answers

8 votes
A straight line is 180°.

The sum of all the angles in a triangle is also 180°.

Let the missing angle be x°.

For the straight line:
x + 2x²+ 3x+ 6 = 180

x = 180 - (2x² + 3x + 6)

x = 180 - 2x² - 3x - 6

x = 174 - 2x² - 3x

For the missing angle in the triangle:
(174 - 2x² - 3x) + 8x + 3x² - 6x = 180

174 - 2x² - 3x + 8x + 3x² - 6x = 180

174 + x² - x = 180

x² - x + 174 - 180 = 0

x² - x - 6 = 0

(x + 2)(x - 3) = 0

x + 2 = 0 or x - 3 = 0
x = -2 or x = 3


The answer is x = -2 or x = 3
User ImpopularGuy
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3.4k points
11 votes

9514 1404 393

Answer:

x = 3

Explanation:

An exterior angle is equal to the sum of the remote interior angles:

2x^2 +3x +6 = (8x) +(3x^2 -6x)

x^2 -x -6 = 0 . . . . . . subtract the left-side expression, put in standard form

(x -3)(x +2) = 0 . . . . .factor

The value of x is a value that makes a factor zero. These factors are zero when x=3 or x=-2. Only positive values of x will give positive angles in this geometry. The only useful solution is ...

x = 3

User Alexander Sigachov
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3.4k points