document.write( "Question 1078613: y is directly proportional to x^2 and y=a for a particular value of x. Find an expression for y in terms of a, when this value of x is doubled.\r
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Algebra.Com's Answer #693253 by KMST(5328)\"\" \"About 
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The phrase \"y is directly proportional to x^2\" means
\n" ); document.write( "\"y=k%2Ax%5E2\" for a some constant \"k\" .
\n" ); document.write( "In that product, if you double x (you replace \"2x\" for \"x\" ),
\n" ); document.write( "you get \"y=k%2A%282x%29%5E2=k%2A2%5E2%2Ax%5E2=k%2A4%2Ax%5E2=4%2A%28kx%5E2%29\" ,
\n" ); document.write( "so you quadruple the value of \"y\" and get \"4a\" .
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