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Select the x-coordinate of the vertex of the parabola defined by the function f(x) = -7x2 + 3x + 5.

a. -7/3
b. 5
c. 3/14
d. -3/7
 

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Francisco E. | Francisco; Civil Engineering, Math., Science, Spanish, Computers.Francisco; Civil Engineering, Math., Sci...
5.0 5.0 (1 lesson ratings) (1)
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the x value for the vertex of a parabola is -b/2a =-3/(-2*7) = 3/14
is the answer, the derivation made by my colleague Piyushi L is perfect as well.  
PIYUSH L. | Maths tutoring for middle school to college maths studentsMaths tutoring for middle school to coll...
5.0 5.0 (6 lesson ratings) (6)
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df(x) / dx should be 0 for the parabola f(x) at the vertex point
 
df(x)/dx = -14x + 3 = 0
 
x = 3/14
 
Answer is c