# Find the equation for the line tangent to the function $f(x) = 2{\sqrt x}$ at $x=25$

Find the equation for the line tangent to the function $f(x) = 2{\sqrt x}$ at $x=25$ Find the slope in two ways:

(i) by using the limit definition of the derivative,

(ii) and using derivative shortcut formulas.

I think was able to find that $p_1= (25,10)$ and bring to use derivative definition, but when I multiply by a "disguised $1$" ,$\frac{2{\sqrt {25+h}}-10}{2{\sqrt {25+h}}-10}$ I'm lost

• calculate this limit $$\lim_{h \to 0} \frac{2 \sqrt{x+h}- 2\sqrt x}{h}$$ then put $x=25$. That gives you slope. – Santosh Linkha Feb 8 '18 at 4:53
• mathjax references to help you typeset maths. – Siong Thye Goh Feb 8 '18 at 4:54