Bonjour,
f(x)= (3x-5)²-(3x-5)(x+4)
Calculer pour :
x= 1
f(1)= (3(1)-5)²-(3(1)-5)((1)+4)= (-2)²-(3-5)(1+4)= 4-(-2)(5)= 4-(-10)= 4+10= 14
x= 4.5
f(4.5)= [ 3(4.5)-5 ]²- [3(4.5)-5 ][4.5+4]= 8.5²-(13.5-5)(8.5)=72.25- (8.5)(8.5)= 0
Question 1
Soit x = 1 :
[tex]f = (3x - 5)x^{2} - (3x - 5) (x+4)[/tex]
= (3 x 1 - 5) x [tex]1^{2}[/tex] - (3 x 1 - 5) (1 + 4)
= (3 - 5) x [tex]1^{2}[/tex] - (3 - 5) x 5
= -2 x [tex]1^{2}[/tex] - (-2) x 5
= -2 + 2 x 5
= -2 + 10
= -8
Question 2
Soit x = 2 :
[tex]f = (3x - 5)x^{2} - (3x - 5) (x+4)[/tex]
= (3 x 2 - 5) x [tex]2^{2}[/tex] - (3 x 2 - 5) (2 + 4)
= (6 - 5) x [tex]2^{2}[/tex] - (6 - 5) x 6
= 1 x [tex]2^{2}[/tex] - 1 x 6
= 4 - 6
= -2
Question 3
Soit x = 4,5 :
[tex]f = (3x - 5)x^{2} - (3x - 5) (x+4)[/tex]
= (3 x 4,5 - 5) x [tex]4,5^{2}[/tex] - (3 x 4,5 - 5) (4,5 + 4)
= (13,5 - 5) x [tex]4,5^{2}[/tex] - (13,5 - 5) x 8,5
= 8,5 x [tex]4,5^{2}[/tex] - 8,5 x 8,5
= 8,5 ([tex]4,5^{2}[/tex] - 8,5)
= [tex]\frac{17}{2}[/tex] ([tex]\frac{x}{y} (\frac{81}{4} - \frac{17}{2} )[/tex]
= [tex]\frac{799}{8}[/tex]
