(9+b³)(9-b³)=81-b^6
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У=ln х-1/х+1y'=1/x+1/(x+1)^2=(x^2+3x+1)/x(x+1)y'=1/x+1/x^2=x^2+x=(1+x)/x^2<span>y'=(2*sqrt(x^2+1)-2x(2x)*(1/2)/sqrt(x^2+1))/(x^2+1)=sqrt(x^2+1)/(x^2+1)^2</span>
(2a+b)d^2=2ad^2+bd^2
(9c)^2-(8b)^2=81c^2-64b^2