document.write( "Question 629638: if the equation x^2-15-k(2x-8)=0has equal roots find the value of k \n" ); document.write( "
Algebra.Com's Answer #396389 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
If the roots are equal, the equation looks
\n" ); document.write( "like \"+%28+x+-+a+%29%5E2+=+0+\", then there are 2 roots
\n" ); document.write( "at \"+x+=+a+\", so I can say
\n" ); document.write( "\"+%28+x+-+a+%29%5E2+=+x%5E2+-+15+-+k%2A%28+2x+-+8+%29+\"
\n" ); document.write( "\"+x%5E2+-+2a%2Ax+%2B+a%5E2+=+x%5E2+-+2k%2Ax+-+15+%2B+8k+\"
\n" ); document.write( "\"+x%5E2+-+2a%2Ax+%2B+a%5E2+=+x%5E2+-+2k%2Ax+%2B+%28+8k+-+15+%29+\"
\n" ); document.write( "Matching up coefficients:
\n" ); document.write( "\"+k+=+a+\"
\n" ); document.write( "\"+a%5E2+=+8k+-+15+\"
\n" ); document.write( "By substitution:
\n" ); document.write( "\"+k%5E2+=+8k+-+15+\"
\n" ); document.write( "\"+k%5E2+-+8k+%2B+15+=+0+\"
\n" ); document.write( "\"+%28+k+-+3+%29%2A%28+k+-+5+%29+=+0+\"
\n" ); document.write( "\"+k+=+3+\"
\n" ); document.write( "\"+k+=+5+\"
\n" ); document.write( "--------
\n" ); document.write( "check answers:
\n" ); document.write( "\"+x%5E2+-+15+-+k%2A%28+2x+-+8+%29+=+0+\"
\n" ); document.write( "\"+x%5E2+-+15+-+3%2A%28+2x+-+8+%29+=+0+\"
\n" ); document.write( "\"+x%5E2+-+15+-+6x+%2B+24+=+0+\"
\n" ); document.write( "\"+x%5E2+-+6x+%2B+9+=+0+\"
\n" ); document.write( "\"+%28+x+-+3+%29%5E2+=+0+\"
\n" ); document.write( "so, \"+k+=+3+\" works
\n" ); document.write( "\"+x%5E2+-+15+-+k%2A%28+2x+-+8+%29+=+0+\"
\n" ); document.write( "\"+x%5E2+-+15+-+5%2A%28+2x+-+8+%29+=+0+\"
\n" ); document.write( "\"+x%5E2+-+15+-+10x+%2B+40+=+0+\"
\n" ); document.write( "\"+x%5E2+-+10x+%2B+25+=+0+\"
\n" ); document.write( "\"+%28+x+-+5+%29%5E2+=+0+\"
\n" ); document.write( "\"+k+=+5+\" works too
\n" ); document.write( "
\n" );