[tex]\displaystyle\bf\\1)\\\\(4a+7)^{2} -16a^{2} =(4a)^{2} -2\cdot 4a\cdot 7+7^{2} -16a^{2}=\\\\=16a^{2} -56a+49-16a^{2} =-56a+49\\\\\\2)\\\\25+(2a-5)(2a+5)=25+(2a)^{2} -5^{2} =25+4a^{2} -25=4a^{2} \\\\\\3)\\\\(3x-1)^{2} +(8+3x)(8-3x)=(3x)^{2} -2\cdot 3x\cdot 1+1^{2} +8^{2} -(3x)^{2} =\\\\=9x^{2} -6x+1+64-9x^{2} =65-6x[/tex]