Bonjour,

Calculer l'inconnue:

• (b+5)/(b+2)= 2/5

2(b+2)= 5(b+5)

2b+4= 5b+25

2b-5b= 25-4

-3b= 21

b=-21/3

b= -7

• 3(t+1)=4(t+2)

3t+3= 4t+8

3t-4t= 8-3

-t= 5

t= -5

• (y-2)/7= 3/(y+2)

(y-2)(y+2)= 7 x 3

y²-2y+2y-4= 21

y²= 21+4

y²= 25 <=> y²= 5² <=> y²-5²= 0

(y-5)(y+5)=0

y-5= 0  ou   y= -5

y= 5     ou   y= 5