What is the square root of 67?

2 Answers
Oct 12, 2016

67 is a prime, and cannot be factored......

Explanation:

.........and thus 67^(1/2) = +-sqrt67.

Feb 19, 2017

sqrt(67) ~~ 34313/4192 ~~ 8.185353

Explanation:

67 is a prime number, so in particular has no square factors. So its square root is irrational and not simplifiable.

There are several methods you can use to find rational approximations.

Here's a method based on the Babylonian method...

To find the square root of a number n, choose an initial approximation p_0/q_0 where p_0, q_0 are integers.

Then apply the following formulas repeatedly to get better approximations:

{ (p_(i+1) = p_i^2+n q_i^2), (q_(i+1) = 2 p_i q_i) :}

In our example, let n = 67, p_0 = 8 and q_0 = 1, since 8^2 = 64 is quite close to 67. Then:

{ (p_1 = p_0^2+n q_0^2 = 8^2+67*1^2 = 64+67 = 131), (q_1 = 2 p_0 q_0 = 2*8*1 = 16) :}

{ (p_2 = p_1^2 + n q_1^2 = 131^2+67*16^2 = 17161+17152 = 34313), (q_2 = 2 p_1 q_1 = 2*131*16 = 4192) :}

If we stop here, we get:

sqrt(67) ~~ 34313/4192 ~~ 8.185353

which is accurate to 6 decimal places.