Réponse :
Exercice 1
f(x)=4x² + x = x(4+x)
k(x)= 2x+4= 2(x+2)
Exercice 2
a) 7x + 21 = 49
7x = 49 - 21
7x = 28
x = 28 : 7 = 4
0,2x - 4 = 8
0,2x = 8-4
0,2x = 4
x = 4 : 0,2 = 20
4x + 48 = 120
4x = 120 - 48
4x = 72
x = 72 : 4 = 18
7 + 5x = 18
5x = 18 - 7
5x = 11
x = 11/5 = 2,2
6x = 2x + 18
6x - 2x = 18
4x = 18
x = 18/4 = 4,5
12x = 4x + 9
12x -4x = 9
8x = 9
x = 9/8 = 1,125
3x + 12 = 8x +9
3x - 8x = 9 - 12
-5x = -3
x = 3/5 = 0,6
13x + 40 = 8x + 40
13x - 8x = 40 - 40
5x = 0
x = 0
Exercice 3
f(x) = 45x² - x^3
f(0) = 0
f(10) = 45 (100) - 1 000 = 3 500
f(20) = 45 (400) - 8 000 = 18 000 - 8 000 = 10 000
f(25) = 45 (625) - 15 625 = 28 125 - 15 625 = 12 500
f(30) = 45 (900) - 27 000 = 40 500 - 27 000 = 13 500
f(35) = 45 (2 025) - 42 875= 91 125 - 42 875 = 48 250
f(40) = 45 (1 600) - 64 000 = 72 000 - 64 000 = 8 000
f(45) = 45 (2 025) - 91 125 = 91 125 - 91 125 = 0
Explications étape par étape
désolée je ne t' ai pas tout fait
