document.write( "Question 400064: Given that f(x) = x^2 + ax + 15 has a minimum value of -12 what is a ? \r
\n" ); document.write( "\n" ); document.write( "think im missing something very simple in solving this problem.
\n" ); document.write( "its suppose to involve only algebra in order to solve but i got completely lost and tried using calculus which got me even more lost -- I was thinking minimum value -12 means lower limit of the parabula is -12 so i solved the derivative of the function to be that x =a/2 kept going for a while and got an answer that made no sense. soooo what am i missing how do i do this problem with just algebra? \n" ); document.write( "

Algebra.Com's Answer #283271 by ewatrrr(24785) $\"\"$ $\"About$

You can put this solution on YOUR website!


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document.write( "Hi
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document.write( "f(x) = x^2 + ax + 15 with a minimum value of -12
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document.write( "f(x) = (x+ a/2)^2 - a^2/4 + 15
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document.write( "Using the vertex form of a parabola,  where(h,k) is the vertex
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document.write( " -a^2/4 + 15 = -12
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document.write( "      27 = a^2/4
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document.write( "      27*4 = a^2
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document.write( "        a = ą sqrt(108) \n" );
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