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How can the following be justified: If 4x + 6 = 20 then 4x = 14 If 2x + 4 = y and y =...

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connorcolin3 | (Level 1) Valedictorian

Posted December 15, 2011 at 12:47 AM via web

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How can the following be justified:

If 4x + 6 = 20 then 4x = 14

If 2x + 4 = y and y = 3x - 6, then 2x + 4 = 3x - 6

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted December 15, 2011 at 12:57 AM (Answer #1)

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It is given that 4x + 6 = 20

Subtract 6 from both the sides

4x + 6 - 6 = 20 - 6

=> 4x = 14

The property used here is the addition property of equality: if a = b, a - c = b - c for all values of a, b and c.

It is given that 2x + 4 = y and y = 3x - 6

As 2x + 4 = y = 3x - 6, 2x + 4 = 3x - 6

The property used here is the transitive property of equality: if a = b and b = c, then a = c.

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