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 #1
avatar+9488 
+2

(x - 1)(x + 2)  =  70

                                      Multiply out the left side of the equation.

x2 + x - 2  =  70

                                      Subtract  70  from both sides of the equation.

x2 + x - 72  =  0

 

Can you think of two numbers add to  1  and multiply to  -72?   →   -8  and  +9 .

So the left side can be factored like this...

 

(x - 8)(x + 9)  =  0           Now we set each factor equal to zero and solve for  x  .

 

x - 8  =  0      or      x + 9  =  0

     x  =  8      or            x  =  -9

 

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I don't know the best way to do the second one, but I'm sure someone else on here does.

Here's the third one:

 

9(x - 1)2  =  4(x - 2)2     Take the ± square root of both sides.

                                     (We only need to write the ± on one side though.)

 

9(x1)2=±4(x2)2 9(x1)2=±4(x2)2 3(x1)=±2(x2)

 

3x3=±(2x4)       Split this into two seperate equations.

 

3x3=+(2x4)or3x3=(2x4) 3x3=2x43x3=2x+4 x3=45x3=4 x=15x=7 x=75

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Sep 27, 2017
 #2
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Sep 27, 2017
 #3
avatar+130466 
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Sep 27, 2017
Sep 26, 2017

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