Respuesta :

hello :
 f(x) = -5x² +x+1
a = -5   b = 1   c = 1 
the vertex is the point A(-b/2a ; f(-b/2a) )    
-b/2a = (-1/-10) = 1/10 = 0.1
f(1/10) = -5(1/10)²+(1/10)+1 =21/20 = 1.05
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