[tex]A = 15x - (x + 7)^{2}[/tex]
[tex]= 15x - ( x^{2} + 49 + 14x )[/tex]
[tex]= 15x - x^{2} - 49 - 14x[/tex]
[tex]= x - x^{2} - 49[/tex]
[tex]B = (\frac{x}{2} - \frac{1}{4})^2[/tex]
[tex]=\frac{x^2}{4} - \frac{2x}{8} + \frac{1}{4}[/tex]
[tex]= \frac{2x^2-2x+2}{8}[/tex]
[tex]= \frac{x^2-x+1}{4}[/tex]
[tex]C = (x + y)^{2} - (x - y)^{2}[/tex]
[tex]= x^2 + 2xy +y^2 - ( x^2 + y^2 - 2xy )[/tex]
[tex]= x^2 + 2xy +y^2 - x^2 -y^2 + 2xy[/tex]
[tex]= 4xy[/tex]
