Question

N=(x+3)² - 2x - (2+x)² este :
A. 2x²+8x
B. 5
C. 5-2x
D. 2x²-2x+5
Help,please !

Answer 1

$(x+3)^2-2x-(2+x)^2= x^{2} +6x+9-2x-4-4x- x^{2} =5$
Raspunsul corect este B. 5

Answer 2

$N=(x+3)^2-2x-(2+x)^2 \\ N=x^2 +2 \cdot x \cdot 3+3^2-2x-(2^2+2 \cdot 2 \cdot x +x^2) \\ N=x^2+6x+9-2x-(4+4x+x^2) \\ N=x^2+6x+9-2x-4-4x-x^2 \\ N=9-4 \\ N=5~(B)$