1) [tex](2x-1)(2x+1)+(x-7)(x+7)=4x^2-1+x^2-49=5x^2-50[/tex]

2)[tex](4x-3y)(4x+3y)+(3x+4y)(4y-3x)=16x^2-9y^2+16y^2-9x^2=5x^2+5y^2[/tex]

3)[tex](2x-3)^2-(x-4)^2=4x^2-12x+9-(x^2-8x+16)=4x^2-12x+9-x^2+8x-16=3x^2-4x-7[/tex]

4)[tex](7a-5b)(7a+5b)-(4a+7b)^2=49a^2-25b^2-(16a^2+56ab+49b^2)=49a^2-25b^2-16a^2-56ab-49b^2=33a^2-74b^2-56ab[/tex]

5)[tex](a+7)^3-8=a^3+21a^2+147a+343-8=a^3+21a^2+147a+335[/tex]