Question

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Answer 1

1. -m(m+2)+(m+3)(m-3)=(-m)^2-2m+m^2-9=-2m-9

при $m=\frac{1}{2}$      $-2*\frac{1}{2}-9=-10$

2. (x-2)(x+2)-x(x-13)=x^2-4-x^2+13x=13x-4

при $x=-\frac{2}{13}$    $13*(-\frac{2}{13})-4= -6$

3. (a-3)^2-a(5a-6)=a^2-6a+9-5a^2+6a=9-4a^2=(3-2a)(3+2a)

при $a=-\frac{1}{3}$  $(3-2*(-\frac{1}{3}))(3+2*(-\frac{1}{3})=(3+\frac{2}{3})(3-\frac{2}{3})=\frac{11}{3}*\frac{7}{3}=\frac{77}{3}=25\frac{2}{3}$