Answer:
r=4
Step-by-step explanation:
15r-6r=36
9r=36
r=36/9
r=4
Marco's equation is correct. Cosine is an even function, which means that for every x, f(-x) = f(x). In other words, you get the same answer for a negative value that you would for its corresponding positive value.
#9 is yes because 12 is double 6. 6+6=12 I don't know #10. Sorry!

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Divide by 2/3 on both sides :
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Change the divide fraction to multiplication fraction :
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Simplify :
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Square root both sides :
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Answer :
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Answer: The smallest possible value of x is -6---------------------------------------------------------------------
I don't know use a calculator