salut
f(x)=((x+5)/2)-x =>(5-x)/2 => -(1/2)x+5/2
g(x)=(x+1)^2-x^2
=x^2+2x+1-x^2 => 2x+1
2) signe de f
x - inf 5 +inf
f(x) + 0 -
signe de g
x - inf -1/2 +inf
g(x) - 0 +
exo 3
1)
f(5)=105 f et de la forme f(x)=ax
f(5)=a*5=105 =>a=21 => f(x)=21x
2)
g(5)=1 et g(3)=-3
a=(-3-1)/(3-5) => a=2
calcul de b
1=5*2+b => b=-9 => g(x)=2x-9
3)
signe de f
x - inf 0 +inf
f - 0 +
signe de g
x - inf 9/2 +inf
g - 0 +
