# Quick easy question.

• Feb 4th 2008, 04:22 PM
white_cap
Quick easy question.
Solve.
l 2x +1 l = 4

I've never done 'exact; values before any help would be awsome. i've got 3/2 and -5/2, or is it 5/2?

Thanks.
• Feb 4th 2008, 05:14 PM
Cursed
Quote:

Originally Posted by white_cap
Solve.
l 2x +1 l = 4

I've never done 'exact; values before any help would be awsome. i've got 3/2 and -5/2, or is it 5/2?

Thanks.

Well, your original answers of ${\frac{3}{2}}$ and $-{\frac{5}{2}}$ are correct.

Basically you have to solve the equation twice. The first time you treat the absolute value as if it were positive, and the second time you treat the absolute value as if it were negative. You do this so you can figure out the positive and negative values that work.

$(2x+1)=4$ and $-(2x+1)=4
$

$| 2({\frac{3}{2}}) + 1 | = 4$

$|4| = 4.$ Correct.
--------------

$| 2(-{\frac{5}{2}}) + 1 | = 4$

$|-4| = 4.$ Correct.
--------------

$| 2({\frac{5}{2}}) + 1 | = 4$

$|6| = 4.$ Wrong.
• Feb 7th 2008, 09:39 AM
pombiux4
Quote:

Originally Posted by white_cap
Solve.
l 2x +1 l = 4

I've never done 'exact; values before any help would be awsome. i've got 3/2 and -5/2, or is it 5/2?

Thanks.

X= 1.5 or 3/2 the other answers are wrong
• Feb 18th 2009, 12:09 PM
mr fantastic
Quote:

Originally Posted by pombiux4
X= 1.5 or 3/2 the other answers are wrong

x = -5/2 is correct. x = 5/2 is not correct. Easily verified by substitution.