Use linear approximation, i.e. the tangent line, to approximate 25.4\displaystyle \sqrt{{{25.4}}} as follows:
Let f(x)=x\displaystyle {f{{\left({x}\right)}}}=\sqrt{{x}}. Find the equation of the tangent line to f(x)\displaystyle {f{{\left({x}\right)}}} at x=25\displaystyle {x}={25}

L(x)\displaystyle {L}{\left({x}\right)} =  

Using this, we find our approximation for 25.4\displaystyle \sqrt{{{25.4}}} is
 
NOTE: For this part, give your answer to at least 9 significant figures or use an expression to give the exact answer.