Ответ:
[tex]7. mn+n^2-3m-3m=n(m+n)-3(m+n)=(n-3)(m+n)=\\(1\frac{1}{3} -3)(4\frac{2}{3}+ 1\frac{1}{3} )=\\(\frac{4}{3} -3)(5\frac{3}{3} )=\\-\frac{5}{3} *6=\\-10.\\\\8. (3x+4)(4x-3)-5=(2x+5)(6x-7)\\12x^{2} -9x+16x-12-5=12x^{2} -14x+30x-35\\7x-17=16x-35\\7x-16x=-35+17\\-9x=-18\\-x=-2\\x=2[/tex]
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Ответ:
[tex]7. mn+n^2-3m-3m=n(m+n)-3(m+n)=(n-3)(m+n)=\\(1\frac{1}{3} -3)(4\frac{2}{3}+ 1\frac{1}{3} )=\\(\frac{4}{3} -3)(5\frac{3}{3} )=\\-\frac{5}{3} *6=\\-10.\\\\8. (3x+4)(4x-3)-5=(2x+5)(6x-7)\\12x^{2} -9x+16x-12-5=12x^{2} -14x+30x-35\\7x-17=16x-35\\7x-16x=-35+17\\-9x=-18\\-x=-2\\x=2[/tex]