Please Help! Urgent!

For it to be the square of a binomial, it has to be in the form:

$(r + s)^2 = 4x^2 + 14x + c$

We find that the first term squared = 4x^2

$r^2 = 4x^2$

$r = 2x$

$(2x + s)^2 = 4x^2 + 14x + c$

We know the second term is in the form:

$4(x)(r) = 14x$

$4r = 14$

$r = 3.5$

So our binomial is in the form:

$(2x+3.5)(2x+3.5)$

So our constant "c" would be:

$c = 3.5^2$

$c = 12.25$

(If this answer is wrong please tell me, as I would be more than happy to fix it)