Question 177981
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Find <i>k</i> such that *[tex \Large 4x^2 + 6.4 x + k] is a perfect square.


Factor out the 4:  *[tex \Large 4(x^2 + 1.6 x + \frac {k}{4})] 


Divide the coefficient on the <i>x</i> term by 2 and square the result:


*[tex \Large (\frac {1.6}{2})^2 = (0.8)^2 = 0.64]


Now we know that *[tex \Large \frac {k}{4} = 0.64]


Hence: *[tex \Large k = 2.56]


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