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

#Algebra

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`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
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Comments

Use the quadratic formula and solve for $r$ .

In fact you get two answers, 13.5 and -6.5

A Former Brilliant Member - 5 years, 1 month ago

Thx man, ur awesome

Jason Chrysoprase - 5 years, 1 month ago

my pleasure :)

A Former Brilliant Member - 5 years, 1 month 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

Ashish Menon - 5 years, 1 month ago

Keep learning. Your passion in math will pay off.

Sal Gard - 5 years ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$