Question 1043620
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First solve for x^2



{{{k = ((x+1)(x-1))/3}}}



{{{3k = 3*(((x+1)(x-1))/3)}}} Multiply both sides by 3



{{{3k = (x+1)(x-1)}}}



{{{3k = x^2-1}}} Use the difference of squares rule



{{{3k+1 = x^2-1+1}}} Add 1 to both sides



{{{3k+1 = x^2}}}



{{{x^2 = 3k+1}}}



Now multiply both sides by 3



{{{x^2 = 3k+1}}}



{{{3x^2 = 3(3k+1)}}}



{{{3x^2 = 9k+3}}}



The final answer is <font color=red size=4>choice D) 9k+3</font>



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