Question 323618
{{{f(x)=x^2 + 3x + 9}}}
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{{{f(x+h)=(x+h)^2+3(x+h)+9}}}
{{{f(x+h)=(x^2+2hx+h^2)+3x+3h+9}}}
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{{{f(x+h)-f(x)=2hx+h^2+3h}}}
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{{{(f(x+h)-f(x))/h=2x+h+3}}}
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{{{lim(x->0,(f(x+h)-f(x))/h=2x+3)}}}