Question

exercitiul 15
45 de puncte +coroana
URGENTT

Answer 1

Răspuns:

f:R-> R ,f(x)=3x²-8x+2

a) abscisa este 1 => x=1 => A(1;y)

y=f(1)=3•1²-8•1+2=-3 => A(1;-3)

b)ordonata este 13=> y=13 => B(x1;13),C(x2;13)

f(x)=13=> 3x²-8x+2=13 => 3x²-8x-11=0 => delta= 64+132=196 =14² => x1 =(8+14)/6 =22/6=11/3 ; x2= (8-14)/6=-1

B(11/3;13), C(-1;13)

Answer 2

$\it f(x)=3x^2-8x+2 \Rightarrow y=3x^2-8x+2\\ \\ a)\ \ x=1 \Rightarrow y=3-8+2=-3 \Rightarrow A(1,\ -3)\in Gf\\ \\ b)\ y=13 \Rightarrow 13=3x^2-8x+2 \Rightarrow 3x^2-8x-11=0 \Rightarrow \\ \\ \Rightarrow 3x^2+3x-11x-11=0 \Rightarrow 3x(x+1)-11(x+1)=0 \Rightarrow \\ \\ \Rightarrow (x+1)(3x-11)=0 \Rightarrow x_1=-1,\ \ x_2=\dfrac{11}{3} \Rightarrow \begin{cases} \it B(-1,\ 13) \in Gf\\ \\ \it C\Big(\dfrac{11}{3},\ 13\Big) \in Gf\end{cases}$