SOLUTION: Find a value for k that will make 4x^2 + 6.4x + k a perfect square. Describe the procedure that you used which requires algebra [that is, not trial and error].

Question 182861: Find a value for k that will make 4x^2 + 6.4x + k a perfect square. Describe the procedure that you used which requires algebra [that is, not trial and error].
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
4x^2 + 6.4x + k
.
Looking at just the terms with 'x':
4x^2 + 6.4x
Factor out 4:
4(x^2 + 1.8x)
.
Take 1/2 of 1.8 and square it, to get:
((1/2)(1.8))^2 = .9^2 = 0.81
.
Adding it in:
4(x^2 + 1.8x + 0.81)
4x^2 + 6.4x + 3.24
.
So, k = 3.24
.
The process above is called "completing the square". For additional info see:
http://www.purplemath.com/modules/solvquad3.htm

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