a² - 3a + b² + 3b - 2ab = (a² - 2ab + b²) - (3a - 3b) = (a - b)² - 3(a - b) =
= (a - b)(a - b - 3);
<span>(а-2)^2-a(3a-4) = a^2 - 4a + 4 - 3a^2+4a = 4 - 2a^2 = 2(2 - a^2) = 2(2 - (-3/2)) = 2(2+3/2))= 2*3,5 = 7</span>
<span>5^x·3^y=135</span>
<span> 3^y-5^x+1=2</span>
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<span>5^x·3^y=135</span>
<span> 3^y-5^x=2-1</span>
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</span>
<span>5^x·3^y=135 Замена переменных 5^x=t , 3^y=u t*u=135</span>
<span> 3^y-5^x=1 u+t=1</span>
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<span>t*u=135</span>
<span> u=1-t</span>
<span>подставляем в первое, имеем:</span>
<span>t(1-t)=135</span>
<span>t-t^2=135</span>
<span>t^2 -t +135=0</span>
<span>D=1-4*135 <0</span>
не имет решений