document.write( "Question 188488: find the vertex, x-intercept, and y-intercept of the parabola given by y=7x^2+21x-378 \n" ); document.write( "

Algebra.Com's Answer #141327 by stanbon(75887) $\"\"$ $\"About$

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find the vertex, x-intercept, and y-intercept of the parabola given by
\n" ); document.write( "y = 7x^2+21x-378
\n" ); document.write( "----------------
\n" ); document.write( "Vertex form:
\n" ); document.write( "7x^2 + 21x = y + 378\r
\n" ); document.write( "\n" ); document.write( "7(x^2 + 3x + (3/2)^2) = y + 378 + 7(9/4)
\n" ); document.write( "7(x+3/2))^2 = y + 393.75
\n" ); document.write( "Vertex: (-3/2 , -393.75)
\n" ); document.write( "-----------------------------------
\n" ); document.write( "Y-intercept:
\n" ); document.write( "Let x= 0, then y = -378
\n" ); document.write( "-----------------------------------
\n" ); document.write( "x-intercept
\n" ); document.write( "Let y = 0 and solve for \"x\".
\n" ); document.write( "x = [-21 +- sqrt(21^2 - 4*7*-378)]/14\r
\n" ); document.write( "\n" ); document.write( "x = [-21 +- 105]/14\r
\n" ); document.write( "\n" ); document.write( "x = [-21 + 105]/14 or x = [-21 - 105]/14\r
\n" ); document.write( "\n" ); document.write( "x = 6 or x = -9
\n" ); document.write( "===========================================
\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "

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