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Fie functia f:R->R , f(x)=2x+3. Rezolvati ecuatia : f(x+1)+f(x-2)=f(x)+5
Ma poate ajuta cineva , va rog!?


Răspuns :

f(x+1)+f(x-2)=f(x)+5
2(x+1)+3+2(x-2)+3=2x+3+5
2x+2+3+2x-4+3=2x+8
4x+4=2x+8
4x-2x=8-4
2x=4
x=2
f:R->R
f(x)=2x+3
f(x+1)+f(x-2)=f(x)+5
f(x+1)=2(x+1)+3=2x+2+3=2x+5
f(x-2)=2(x-2)+3=2x-4+3=2x-1
f(x+1)+f(x-2)=f(x)+5
⇒2x+5+2x-1=2x+3+5
⇒4x+4=2x+8
4x-2x= -4+8
2x=4
x=4:2
x=2