SOLUTION: z(z-9)=-20

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Question 237615: z(z-9)=-20
Found 2 solutions by nyc_function, College Student:
Answer by nyc_function(2741) About Me  (Show Source):
You can put this solution on YOUR website!
z(z-9)=-20
z^2 - 9z = - 20
z^2 - 9z + 20 = 0
What two numbers when multiplied together will yield 20 but when added will yield -9?
How about -4 times -5?
(z - 4)(z - 5) = 0
Set each factor to zero and solve for z individually.

z - 4 = 0
z = 4

z - 5 = 0
z = 5
Solution: z = 4 and z = 5

Answer by College Student(505) About Me  (Show Source):
You can put this solution on YOUR website!
Steps:
To abtain a quadratic equation from this equation you must
a. multiply z by the contents in the parenthesis
b. move the -20 to the left side of equation
c. let equation equal to zero
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Problem:
z(z-9)=-20
z^2-9z=-20
z^2-9z+20=0