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 ! :)
