formula x=

Question

The expression 3x2 – 6x – 105 can be used to model the height of a ball thrown in the air after x seconds. Use the quadratic formula provided below to Xigure out how long will ittakefortheballtohittheground.Use a=3, b=-6, and c=-105.Providethe positive solution only.

 

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Answer 1

3x2 – 6x – 105=0

(3x-21)(x+5)=0

3x-21=0; x+5=0

x=21/3=7;   x=-5

 

discard the negative solution. 

 

X=7 seconds