document.write( "Question 70792: f(x)= 72x^2+ 13x-15 how do i graph this function by hand and find the x and y interceptsand the vertex as well as any other points plotted \n" ); document.write( "

Algebra.Com's Answer #50561 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Pick some x-values that will help you. The best ones are
\n" ); document.write( "x = 0
\n" ); document.write( "x = +1
\n" ); document.write( "x = -1
\n" ); document.write( "Then compute the y-value that goes with each x-value
\n" ); document.write( "In this case,
\n" ); document.write( "x = 0, y = -15
\n" ); document.write( "x = +1, y = 70
\n" ); document.write( "x = -1, y = 44
\n" ); document.write( "The y-intercept is -15 as you can see
\n" ); document.write( "To find the x-intercept, make y=0 and find x
\n" ); document.write( "with the quadratic formula
\n" ); document.write( " $\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"$
\n" ); document.write( "this gives you 2 values for x because of the +/- in front
\n" ); document.write( "of the square root
\n" ); document.write( "Your equation is in the form $\"y+=+ax%5E2+%2B+bx+%2B+c\"$
\n" ); document.write( "a = 72
\n" ); document.write( "b = 13
\n" ); document.write( "c = -15
\n" ); document.write( "The vertex will be the value which is exactly between
\n" ); document.write( "the the x-values that make y=0, and that is $\"-b%2F2a\"$ \n" ); document.write( "

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