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An algebraic expression of the form $a + bx$ has the value of $15$ when $x = 2$ and the value of $3$ when $x = 5$. Calculate $a + b$.

 Oct 23, 2017
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a + b (2)  = 15

 

a + b (5) = 3      subtract the second equation  from the first   and we have

 

     -3b  = 12      divide both sides by -3

 

         b =  -4

 

Sub this into the first equation and we have

 

a + -4(2)  = 15

 

a - 8  =  15          add 8 to both sides

 

a  =  23

 

So    a + b  =   23 + (-4)  =   19

 

 

cool cool cool

 Oct 23, 2017

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