Homework Help

Solve: (m - 3)(m - 4) = 20 (there are two answers)

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mattlimey | Student, Grade 11 | (Level 2) Honors

Posted April 15, 2013 at 2:21 AM via web

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Solve:

(m - 3)(m - 4) = 20

(there are two answers)

2 Answers | Add Yours

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted April 15, 2013 at 2:35 AM (Answer #1)

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`(m - 3)(m - 4) = 20`

`m^2-4m-3m+12-20 = 0`

`m^2-7m-8 = 0`

`m^2-8m+m-8 = 0`

`m(m-8)+1(m-8) = 0`

`(m-8)(m+1) = 0`

 

So the answers are;

`m = 8`

`m = -1`

 

Since we have a quadratic function we only have two solutions.

 

Sources:

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oldnick | (Level 1) Valedictorian

Posted April 15, 2013 at 3:48 PM (Answer #2)

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`(m-3)(m-4)=20`

`(m-3)(m-3-1)=20`

`(m-3)^2-(m-3)= 20`

`(m-3)^2-(m-3) -20=0`

`(m-3)^2-2 1/2(m-3) +1/4 -81/4=0`

`(m-3-1/2)^2=81/4`

`(m-7/2)^2=81/4`

using square root both sides:

`m-7/2=+-9/2`

`m=(7+-9)2```

`m_1= 8`   `m_2=-1`

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