bonjour,
(x-5)(1260/x + 1,20) = 1260
1260/x + 1,20x -6300/x - 6 = 1260
1260x/x + 1,2x²/x - 6300x - 6x/x = 1260x/x
1,2x²+1254x-6300x = 1260x
1,2x²-6x-6300x = 0
b²-4ac = (-6)²-4(1,2*-6300) = 36+30240 = 30276
Δ≥0⇒2solutions
√Δ = 174
(-b-√Δ)/2a = (6-174)/2,40 = -70
(-b+√Δ)/2a = (6+174)/2,4 =75
on cherche un nombre d'élèves⇒75
il y avait 75 élèves
