Question 1118185
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The necessary and sufficient condition is 


<pre>
    the discriminant of the quadratic equation is zero:  d = b^2 - 4ac = 0,

    referring to the standard form of the quadratic equation ax^2 + bx + c = 0.



In your case b= 2,  c= 4,  therefore the discriminant d = {{{2^2 - 4*a*4}}} = 4 - 16a.


The condition d= 0 gives you an equation  4 - 16a = 0,   or   16a = 4,

which implies   a = {{{1/4}}} = 0.25.


It is your


<U>Answer</U>.  a = {{{1/4}}} = 0.25.
</pre>

Solved.


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To get introductory knowledge on quadratic equations, see the lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/Introduction-Into-Quadratics.lesson>Introduction into Quadratic Equations</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/proof-of-quadratic-by-completing-the-square.lesson>PROOF of quadratic formula by completing the square</A>

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