Réponses

  • carys
  • Modératrice confirmée
2013-03-05T14:54:52+01:00

1) d = 0.007v² + 0.8v

d = 0.007 * 90² + 0.8 * 90

d = 0.007 * 8100 + 72

d = 56.7 + 72

d = 128.7

 

2) d = 0.007v² + 0.8v

d = 0.007 * 80² + 0.8 * 80

d = 0.007 * 6400 + 64

d = 44.8 + 64

d = 108.8

 

3) d = 0.007v² + 0.8v

50 = 0.007v² + 0.8v

0 = 0.007v² + 0.8v - 50

 

 

On a le trinôme 0.007v² + 0.8v - 50 donc

Δ = b² - 4ac = 0.8² - 4*0.007*(-50) = 0.64 + 1.4 = 2.04 > 0 il y a 2 solutions

 

x1 = (-b + √Δ)/2a = (-0.8 + √2.04)/2*0.007 = (-0.8 + √2.04)/0.014

x2 = (-b - √Δ)/2a = (-0.8 - √2.04)/2*0.007 = (-0.8 - √2.04)/0.014

4) d = 0.007v² + 0.8v

100 = 0.007v² + 0.8v

0 = 0.007v² + 0.8v - 100

 

On a le trinôme 0.007v² + 0.8v - 100 donc

Δ = b² - 4ac = 0.8² - 4*0.007*(-100) = 0.64 + 2.8 = 3.44 > 0 il y a 2 solutions

 

x1 = (-b + √Δ)/2a = (-0.8 + √3.44)/2*0.007 = (-0.8 + √3.44)/0.014

x2 = (-b - √Δ)/2a = (-0.8 - √3.44)/2*0.007 = (-0.8 - √3.44)/0.014

 

voilà voilà ! :)