Solve x2+8x+1>−2x2+2x−2.
Antwoord 1 correct
Correct
Antwoord 2 optie
x=−1
Antwoord 2 correct
Fout
Antwoord 3 optie
x>−1
Antwoord 3 correct
Fout
Antwoord 4 optie
x<−1
Antwoord 4 correct
Fout
Antwoord 1 optie
All x except x=−1
Antwoord 1 feedback
Correct: x2+8x+1>−2x2+2x−2⇔3x2+6x+3>0.
Define f(x)=3x2+6x+3. We determine f(x)=0:
We use the quadratic equation. The discriminant is D=0, which implies that there is only one solution, x=−1.
Via the sign chart (for instance with f(−2)=3 and f(0)=3) we find that f(x) is strictly positive for all x expect for the zero x=−1.
Go on.
Define f(x)=3x2+6x+3. We determine f(x)=0:
We use the quadratic equation. The discriminant is D=0, which implies that there is only one solution, x=−1.
Via the sign chart (for instance with f(−2)=3 and f(0)=3) we find that f(x) is strictly positive for all x expect for the zero x=−1.
Go on.
Antwoord 2 feedback
Wrong: (−1)2+8(−1)+1=−6≯−6=−2(−1)2+2(−1)−2.
Try again.
Try again.
Antwoord 3 feedback
Wrong: Pay attention to the sign chart.
Try again.
Try again.
Antwoord 4 feedback
Wrong: Pay attention to the sign chart.
Try again.
Try again.