Daca x+y=5 si x^2-y^2=45,atunci valuarea expresiei 5y-5x este egala cu:


Răspuns :

x²-y²=45

(x-y)(x+y)=45
(x-y)*5=45

x-y=45:5
x-y=9

-(y-x)=9
y-x = -9

5y-5x=5(y-x)= 5* (-9)= -45
x+y=5
x²-y²=45

x²-y²= (x+y)(x-Y)=5(x-y)=45
=>5x-5y=45

=>-45 =5x-5y