bonjour
C (x) = 4 x ( 1 - 3 x ) + ( 3 x + 1 ) ( 4 x + 3 )
= 4 x - 12 x² + 12 x² + 9 x + 4 x + 3
= 17 x + 3
B = 1/2 ( 1/3 - 1 /5 ) + 2/15
= 1/2 ( 5/15 - 3 /15) + 2 /15
= ( 1/2 * 2/15) + 2 /15
= 2/30 + 2 /15
= 2/30 + 4/30
= 6/30 = 1/5
A = 1 + 1/3 x 1/4
= 1 + 1/12
= 12/12 + 1 /12 = 13/12