[tex] {(2x + 1)}^{2} - 2 {(x - 1)}^{2} + (1 - x)(x + 3)[/tex]
[tex] = 4 {x}^{2} + 4x + 1 - 2( {x}^{2} - 2x + 1) + (x + 3 - {x}^{2} - 3x)[/tex]
[tex] = 4 {x}^{2} + 4x + 1 - 2 {x}^{2} + 4x - 2 + x + 3 - {x}^{2} - 3x[/tex]
[tex] = {x}^{2} + 6x + 2[/tex]
[tex]{(x+3)}^2-7={x}^{2}+6x+9-7={x}^{2}+6x+2