Question

punkt a (6,0) nalezy do wykresu funkcji y = ax² + 5x + 12

oblicz f(-3½)

Answer 1

punkt a (6,0) nalezy do wykresu funkcji y = ax² + 5x + 12

oblicz f(-3½)

 

y = ax² +5x +12

A = (6,0) ---->  x = 6, y = 0

 

0 = a*6² + 5*6 +12

 

36a + 30 +12 = 0

36a + 42 = 0

36a = -42     /:36

  a = (-42 ): 36

a = - 7/6

 

f(x) = y = -7/6x² +5x +12

 

Obliczam  f(-3½)

f(-3½) = f(-7/2) = (-7/6)*(-7/2)² +5*(-7/2) +12

f(-3½) =f(-7/2) = (-7/6)*(49/4) - (35/2) + 12

f(-3½) =f(-7/2) = (-343/24) - (420/24) + (288/24)

f(-3½) =f(-7/2) = -475/24