SOLUTION:
Let whole number = x
x + 2x^2 = 21
2x^2 + x - 21 = 0
2x^2 + 7x - 6x - 21 = 0
x ( 2x + 7 ) - 3 ( 2x + 7 ) = 0
( 2x + 7 ) ( x - 3 ) = 0
2x + 7 = 0
2x = - 7
x = - 7 / 2
OR
x - 3 = 0
x = 3
ANSWER:
Therefore, as 3 is a whole number while - 7 / 2 isn't a whole number, the whole number must be 3.
Hope this helps! :)
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Since the interior is 170 the exteriro must be 10 degrees. There is a total of 360 degrees so 360/10=36 or 36 sides.
Answer: 17
Step by step : 146+2x=180
2x=34
X=17
