# Thread: find to three terms the square root

1. ## find to three terms the square root

Q: find to three terms the square root
a) $1+ 4x$

The problem is that i am trying to use the idea of using an identity such as $a^2+2ab+c^2$ to help find the answer based on trial and error such as $(1 + \frac{2}{x} + x)^2$
but i cannot did the right answer
I'm not clear on what you are doing. What does it mean to "find the square root of 1+ 4x to three terms"? What are "terms" here? I suspect that you are meant to expand $\displaystyle \sqrt{1+ 4x}$ in a power series and keep the first three terms. You could use "MacLaurin series" with $\displaystyle f(x)= (4x+ 1)^{1/2}$ and keep the first three 'terms'.