salut
1) BD²= DC²+BC²
= 8²+6²
= 100
BD= racine(100)= 10
2) AP/AD=AM/AB
=>AP/6=x/8
=> 8*AP= 6x => AP= (3/4)x
3) AM/AB=PM/BD
=> x/8=PM/10
=> 8*PM=10x
=> PM= (10/8)x
4) DP= 6-(3/4)x
MB= 8-x
P_1=> périmètre AMP
=> x+(3/4)x+(10/8)x = 3x
P_2=> périmètre PMBD
=> PM+MB+BD+DP
=> (10/8)x+8-x+10+6-(3/4)x= (48-x)/2 soit 24-(1/2)x
P_1=P_2
=> 3x= 24-(1/2)x
=> 3x+(1/2)x=24
=> (7/2)x=24
=> x= 48/7 environ 6.85