You can put this solution on YOUR website! Find the value for k that will make 4x^2+6.4x +k a perfect square.
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Take the coefficient 'b' and divide by 2:
3.2
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Square the number:
10.24 (this is the value of k)
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Therefore,
4x^2+6.4x +10.24
(2x+3.2)(2x+3.2)
(2x+3.2)^2