表达式5: left parenthesis, "b" , "f" left parenthesis, "b" , right parenthesis , right parenthesisb,fb
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表达式6: "b" equals negative 1.4 4b=−1.44
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Next I need the line of tangency. The slope will be the derivative of f (label it g), and I'll write the equation of the line in point-slope form to avoid the algebra.
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表达式8: "g" left parenthesis, "x" , right parenthesis equals StartFraction, "d" Over "d" "x" , EndFraction "f" left parenthesis, "x" , right parenthesisgx=ddxfx
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表达式9: "y" minus "f" left parenthesis, "b" , right parenthesis equals "g" left parenthesis, "b" , right parenthesis left parenthesis, "x" minus "b" , right parenthesisy−fb=gbx−b
