8. Решите уравнение: a) x²+(5-x)(5+x)=100x; б) (4x+1)²-16(x+2)(x-2) = 17.

a) $$x^2 + (5-x)(5+x) = 100x$$; $$x^2 + 25 - x^2 = 100x$$; $$25 = 100x$$; $$x = \frac{25}{100} = \frac{1}{4} = 0.25$$. б) $$(4x+1)^2 - 16(x+2)(x-2) = 17$$; $$16x^2 + 8x + 1 - 16(x^2 - 4) = 17$$; $$16x^2 + 8x + 1 - 16x^2 + 64 = 17$$; $$8x + 65 = 17$$; $$8x = -48$$; $$x = -\frac{48}{8} = -6$$.