bonjour,
1) Aire de TRI = [( 2 x + 1) ( 2 x) ] /2 = (4 x² + 2 x ) / 2 = 2 x² + 2
Aire RECT = ( 2 x + 1 ) ( 3 x + 2 ) = 6 x² + 4 x + 3 x + 2 = 6 x² + 7 x + 2
2 ) RECTI = 2 x² + 2 + 6 x² + 7 x +2 = 8 x² + 7 x + 4
pour x = 3
RECTI = 8*3² + 7 *3 + 4 = 72 + 21 + 4 = 97 cm²