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Решите задачу:

$(8+y)(y-8)=(y+8)(y-8)=y^2-64\\\\(a+\frac{2}{3}b)(a-\frac{2}{3}b)=a^2-\frac{4}{9}b^2\\\\(\frac{4}{15}n-m)(\frac{4}{15}n+m)=\frac{16}{225}n^2-m^2\\\\(-4a+3b)(3b+4a)=9b^2-16a^2\\\\(\frac{5}{4}c+\frac{3}{7}d)(\frac{3}{7}d-\frac{5}{4}c)=\frac{9}{49}d^2-\frac{25}{16}c^2\\\\(\frac{1}{5}a+\frac{1}{9}b)(\frac{1}{9}b-\frac{1}{5}a)=\frac{1}{81}b^2-\frac{1}{25}a^2$