Need help solving math problem

Test Preparation SAT Preparation
1

<p>The problem is :
x^2+kx+4= (x+c)^2
In the equation above ,k and c are positive constants. so what is the value of k?</p>

<p>I solved the problem in time consuming manner and was wondering if someone could share their way of solving this problem.?
BTW this problem is #16 on the 2007 PSAT</p>

2

<p>x^2 + kx + 4 = x^2 + 2cx + c^2</p>

<p>c^2 = 4</p>

<p>c = 2</p>

<p>2c = k</p>

<p>k = 4</p>

3

<p>Ok thank you very much!</p>