# Math

Please observe the solution for the following two problems :

(a) 2x + 18 = x + 25
(b) 3x + 5 = 7x - 15

(a)

2x + 18 = x + 25
2x - x = 25 - 18. -------- (1)
x = 7

(b)

3x + 5 = 7x - 15
7x - 3x = 15 + 5 ---------- (2)
4x = 20
x = 5

Explain the rules involved in transposing -

In (1)
Can 2x - x = 25 - 18
be expressed as
x - 2x = 18 - 25

In (2)
Can 7x - 3x = 15 + 5
be expressed as
3x - 7x = 15 - 5

If yes - why ?
If no - why not ?

Hope I have framed my question properly. I'm confused with transposing.

1. 👍 0
2. 👎 0
3. 👁 120
1. 1. yes ... it is the result of multiplying the equation by -1

2. no ... the left side can come from multiplication by -1
BUT ... changing a single sign in the right side polynomial is not a legitimate operation

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posted by R_scott
2. Can 7x - 3x = 15 + 5
be expressed as
3x - 7x = 15 - 5

NO !!!!!!!!!!!!!!!!!!!!
7x - 3x = 15 + 5
multiply both sides of the equation by -1
-1(7x-3x) = -1(15+5)
3x - 7x = -15 - 5 *****note -15 not +15

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2. 👎 0
posted by Damon
3. In (1)
Can 2x - x = 25 - 18
be expressed as
x - 2x = 18 - 25
===========================
multiply both sides by -1 again
-2x +x = -25 + 18
sure, fine

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2. 👎 0
posted by Damon
4. Thanks a lot all of you.

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2. 👎 0
posted by Learn

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