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An equation is shown.

3x − 10x + 5 = 5x + 17

What is the value of x that makes the equation true?

User Kelevandos
by
8.2k points

1 Answer

2 votes

Answer:

-1

Explanation:

You want the value of x that is a solution to 3x − 10x + 5 = 5x + 17.

Solution

It can be convenient to subtract the left side of the equation from both sides:

(3x -10x +5) -(3x -10x +5) = (5x +17) -(3x -10x +5) . . . . subtract (3x -10x +5)

0 = (5 -3 +10)x +(17 -5) . . . . . group like terms

0 = 12x +12 . . . . . . . . . . . simplify

0 = x +1 . . . . . . . . . . . divide by 12

-1 = x . . . . . . . . . . . subtract 1

The value of x that makes the equation true is -1.

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Additional comment

You might be told to solve this by simplifying it first to -7x+5 = 5x+17. This is recognizable as a 3-step equation, which might ordinarily be solved by the 3 steps ...

  1. subtract 5x ⇒ -12x +5 = 17
  2. subtract 5 ⇒ -12x = 12
  3. divide by -12 ⇒ x = -1

The first two steps can be combined to "subtract (5x+5)". The result is a negative coefficient on x. That coefficient could be positive by "add (7x-17)" instead, to get -12 = 12x.

User Mandrek
by
7.1k points

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