Question

2) E(x) = (2x+1)² - (x-1)² + (x-2) (x+2) - 3x²+14
a) aratati ca E(x) = x²+6x+10
b) calculati val. lui E(x) pentru ca x=-3
c) aratati ca E(x)>0

Answer 1

a)
E(x)=4x² +4x +1 -x²+2x -1 + x² -4 -3x² +14= x² +6x +10

b) E(-3) = 9 - 18 +10 = 1
c) E(x) = x² +6x + 10 = x² + 6x + 9 +1 = (x+3)² +1  > 0

Answer 2

E(x)= 4x²+4x+1-(x²-2x+1)+x²-4-3x²+14
= 4x²+4x+1-x²+2x-1-3x²+14
=x²+6x+10

x=-3⇒3²+6·3+10=9+18+10=37

37>0