Réponses

2013-03-27T14:14:41+01:00

K = (x+15)²-(x-15)²

K = (x+15+x-15)(x+15-x+15)

K = 2x * 30

K = 60x

 

 1215²-1185²

= (1215+1185)(1215-1185)

= 2400 * 30

= 72000

 

Voilà.. ! j'espère que je t'ai aider

2013-03-27T14:35:53+01:00

K = (x+15)²-(x-15)² <=> K = (x+15+x -15)(x+15-x+15)

         <=> K = x² + 15x - x² + 15x + 15x + 225 - 15x + 225 + x² +15x - x² + 15x - 15x -225 +15x - 225

         <=> K = 60x