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# Help : Algebra

$$87.75 = R^2 - 7R$$

How to get $$R$$ ?

I tried many times but i didn't get it

The answer is $$13.5$$ but i don't know how to get it

Note by Jason Chrysoprase
1 year, 7 months ago

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Use the quadratic formula and solve for $$r$$.

In fact you get two answers, 13.5 and -6.5

- 1 year, 7 months ago

Thx man, ur awesome

- 1 year, 7 months ago

my pleasure :)

- 1 year, 7 months ago

@Jason Chrysoprase You may refer to this wiki to learn them more effectively. :V Anyways, one typo, your heading; change it into Help:Algebra currently it is Help:Algera, ;P

- 1 year, 7 months ago

Keep learning. Your passion in math will pay off.

- 1 year, 5 months ago