Bonsoir,
B = ( 6x -3 ) ( 4x + 1 ) + ( 2x - 5 ) ( 2x + 5 )
B = 24x² + 6x - 12x - 3 + 4x² + 10x - 10x - 25
B = 24x² + 4x² + 6x - 12x + 10x - 10x - 3 - 25
B = 28x² - 6x - 28
C = ( 4x + 1 )² + ( 4x - 5 ) ( x + 1 )
C = 16x² + 8x + 1 + 4x² + 4x - 5x - 5
C = 16x² + 4x² + 8x + 4x - 5x + 1 - 5
C = 20x² + 7x - 4
D = ( 5x + 7 )² + ( 5x - 7 )²
D = 25x² + 70x + 49 + 25x² - 70x + 49
D = 25x² + 25x² + 70x - 70x + 49 + 49
D = 50x² + 98