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2z^2-11z-21

Guest Apr 5, 2017

Best Answer 

 #2
avatar+7324 
+2

To factor this:

2z2 - 11z - 21

 

Split the middle term.

What two numbers add to -11 and multiply to (-21)(2)= -42 ? → -14 and 3

2z2 - 14z + 3z - 21

 

(2z2 - 14z) + (3z - 21)

 

Factor a 2z out of the first term and factor a 3 out of the second term.

2z(z - 7) + 3(z - 7)

 

Factor a (z - 7) out of both terms.

(2z + 3)(z - 7)

hectictar  Apr 5, 2017
 #1
avatar+7481 
+1

2z^2-11z-21

 

\(2z^2-11z-21\)

 

\(z = {11 \pm \sqrt{121+168} \over 4}=\frac{11\pm 17}{4}\)

\(z_1=7\\z_2=-1.5\)

 

\(2z^2-11z-21=2 \times(z-7)\times (z+1.5)\)

 

laugh  !

asinus  Apr 5, 2017
edited by asinus  Apr 5, 2017
 #2
avatar+7324 
+2
Best Answer

To factor this:

2z2 - 11z - 21

 

Split the middle term.

What two numbers add to -11 and multiply to (-21)(2)= -42 ? → -14 and 3

2z2 - 14z + 3z - 21

 

(2z2 - 14z) + (3z - 21)

 

Factor a 2z out of the first term and factor a 3 out of the second term.

2z(z - 7) + 3(z - 7)

 

Factor a (z - 7) out of both terms.

(2z + 3)(z - 7)

hectictar  Apr 5, 2017

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