Monday
May 20, 2013

# Homework Help: Math

Posted by Alli on Sunday, September 4, 2011 at 3:37pm.

if x^13 = j and x^12 = 4/9, which of the following is an expression for x in terms of j?
a. 9/4 j
b. 4/9 j
c. 4j
d. 9j
e. 13j

• Math - Bosnian, Sunday, September 4, 2011 at 4:04pm

x^13 = j Divide both sides with x

x^13 / x = j / x

( Remark: x^13 / x = x^12 )

x^12 = j / x

x^12 = 4 / 9

j / x = 4 / 9 Multiply both sides with 9

9 j / x = 4 Multiply both sides with x

9 j = 4x Divide both sides with 4

9 j / 4 = x

x = 9 j / 4

x = ( 9 / 4 ) j

• Math - bobpursley, Sunday, September 4, 2011 at 4:08pm

x^12 * x=x^13
4/9 * x=j
divide both sides by 4/9

x= 9j/4

This is a very poor question, as the letter j is very often used as the square root on -1, and because of that, it should never be used as a variable.

The same thing applies for i, another symbol for sqrt-1.

Why are i and j both used as symbols for sqrt -1? Because in writing i, it is often confused for 1. See http://en.wikipedia.org/wiki/Imaginary_unit

• Math - Nick, Sunday, September 4, 2011 at 4:16pm

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