Bonsoir
Dans chaque cas, f est une fonction affine.
y = ax + b
Retrouver son expression algébrique.
1. f(5)=10 et f(10)=11
a = [f(10) - f(5)]/(10 - 5)
a = (11 - 10)/5
a = 1/5
10 = 5 * 1/5 + b
10 = 1 + b
b = 10 - 1 = 9
y = x/5 + 9
2. f(−7)=4 et f(4)=−7
a = [f(4) - f(-7)]/(4 - (-7))
a = (-7 - 4)/(4 + 7)
a = (-11)/11
a = (-1)
4 = -7 * (-1) + b
b = 4 - 7 = -3
y = -x - 3
3. f(−8)=0 et f(−1)=13
a = (13 - 0)/(-1 - (-8))
a = 13/(-1 + 8)
a = 13/7
13 = -1 * 13/7 + b
b = 13 + 13/7
b = 91/7 + 13/7 = 104/7
y = 13x/7 + 104/7
4. f(−1)=−5 et f(2)=−9
a = (-9 - (-5))/(2 - (-1))
a = (-9 + 5)/(2 + 1)
a = (-4)/3
-5 = -4/3 * (-1) + b
b = -5 - 4/3
b = -15/3 - 4/3
b = -19/3
y = -4x/3 - 19/3
