calculer astucieusement (-75)x(-0,25)x(+2)x(+4) et (+0,01)x(-25)x(-13,2)x4x(-3)

 (-75)x(-0,25)x(+2)x(+4) 
-75x 2 x -0.25 x4
-150 x -1
= 150

 (+0,01)x(-25)x(-13,2)x4x(-3)
-25 x 4 x 0.01  x -13.2 x -3
-100 x 0.01 x  -13.2 x -3
- 1 x -13.2 x -3
- 39.60

-75x-0,25x2x4
= -75x2x-0,25x4
= -150x-1
= 150

0,01x-25x-13,2x4x-3
= 0,01x-25x4x-13,2x-3
= 0,01x-100x-13,2x-3
=-1x13,2x3
=  -39,6