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# P2 Modulus watch

1. if u have a modulus expression say

l 3x+5 l = l 5x l

do you have to square both sides to solve, or do you just treat the mod bit as brackets

or wqhat if you have one\side with a modulus bit
eg solve for x, in terms of a:
3a = l x-(4x+a) l +a

i get x= 2a(1-a)/(1-4a)

could someone post some more examples with solutions of different types of mod equation questions
2. (Original post by hihihihi)
if u have a modulus expression say

l 3x+5 l = l 5x l

do you have to square both sides to solve, or do you just treat the mod bit as brackets

or wqhat if you have one\side with a modulus bit
eg solve for x, in terms of a:
3a = l x-(4x+a) l +a

i get x= 2a(1-a)/(1-4a)

could someone post some more examples with solutions of different types of mod equation questions
you can square them or draw a graph,depends on how much algebra u want to do..............
3. (Original post by hihihihi)
if u have a modulus expression say

l 3x+5 l = l 5x l

do you have to square both sides to solve, or do you just treat the mod bit as brackets

or wqhat if you have one\side with a modulus bit
eg solve for x, in terms of a:
3a = l x-(4x+a) l +a

i get x= 2a(1-a)/(1-4a)

could someone post some more examples with solutions of different types of mod equation questions
² ³ ± ÷ ° √ ∂ ∞ ≈ ≠ ≡ ≥ ≤ ø Ø ½ ¼ « » µ π

l 3x+5 l = l 5x l
Square both sides:
9x²+30x+25=25x²
16x²-30x-25=0
(8x+5)(2x-5)
Therefore solutions are:
x=-5/8 or x=5/2

3a = l x-(4x+a) l +a
2a = l x-(4x+a) l
±2a = x-(4x+a) therefore:

3a+3x=0
OR
-a+3x=0
4. (Original post by Bhaal85)
² ³ ± ÷ ° √ ∂ ∞ ≈ ≠ ≡ ≥ ≤ ø Ø ½ ¼ « » µ π

3a = l x-(4x+a) l +a
2a = l x-(4x+a) l
±2a = x-(4x+a) therefore:

3a+3x=0
OR
-a+3x=0
I don't understand the ±2 in the bold bit??? Where did that come from
5. (Original post by Silly Sally)
I don't understand the ±2 in the bold bit??? Where did that come from
The modulus can be switched, e.g.

a = l x l is the same as saying:
±a = x
6. (Original post by Bhaal85)
The modulus can be switched, e.g.

a = l x l is the same as saying:
±a = x
ahh - i see! thanks!!!
7. (Original post by Silly Sally)
ahh - i see! thanks!!!
Though in the case of:

l a l = l x l you can't do it.
8. (Original post by Bhaal85)
Though in the case of:

l a l = l x l you can't do it.

WHY NOT?
9. l 3x+5 l = l 5x l
Squaring both sides gives...

9x^2 + 30x +25 = 25x^2
Collecting like terms...

16x^2 - 30x -25.

Factorising...
(8x + 5) (2x - 5)

x = -5/8 or 5/2...

So why was everyone jabbering about an a??? That's the method I would use...Drawing graphs is too time consuming and often far less accurate...

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