Répondre :
On considère l'expression A= 1/4[(x+y)²-(x-y)²] .
A= 1/4[(x+y)²-(x-y)²]
=1/4(x²+2xy+y²-x²+2xy-y²)
=1/4(4xy)
=xy
Calculer A pour :
1. x=3/5 et y=20/9
A=3/5*20/9
=60/45
=4/3
2. x=7^10 et y=7^-15
A=(7^10)*(7^-15)
=7^(-5)
=1/16807
A= 1/4[(x+y)²-(x-y)²]
=1/4(x²+2xy+y²-x²+2xy-y²)
=1/4(4xy)
=xy
Calculer A pour :
1. x=3/5 et y=20/9
A=3/5*20/9
=60/45
=4/3
2. x=7^10 et y=7^-15
A=(7^10)*(7^-15)
=7^(-5)
=1/16807