Question

(X+1)^2+3(X+5)-12=(X+2)^2+3

Answer 1

x^2 + 2 + 3x + 15 -12 = x^2 + 4 + 3
x^2 + 3x+ 5 = x^2 + 7
x^2 - X^2 + 3x + 5 +7 = 0
3x + 12 = 0
3x= -12
x= -4

Answer 2

Folosesti formula de calcul prescurtat ( a + b )^2 = a^2 + 2ab + b^2 si distributivitatea inmultirii fata de adunare c( d + e ) = cd + ce ;
In membrul stang  al ecuatiei obtii x^2 + 2x + 1 + 3x + 15 - 12 = x^2 + 5x + 4 ;
In membrul drept al ecuatiei obtii x^2 + 4x + 4 + 3 = x^2 + 4x + 7 ;
Atunci ai x^2 + 5x + 4 = x^2 + 4x + 7 <=> 5x + 4 = 4x + 7 <=> x + 4 = 7 <=>
 x = 3 => S = { 3 }.

Bafta !