Investigate {x3+x2+10x,x<0−3sinx,x≥0 at x=0 for local maxima / minima.
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Solution
{x3+x2+10x,x<0−3sinx,x≥0 forx≥0 f(x)=−3sinx f′(x)=−3cosx f′(0)=−3 forx<0 f(x)=x2+x2+10x f′(x)=3x2+2x+10 f′(0)=10 f′(x)>forx<0andf′(x)<0forx≥0 f(x) has maxima at x=0