Which of the following is equal to the average (arithmetic mean) of ~$\left ( x+2 \right )^{2}$~ and ~$\left ( x-2 \right )^{2}$~ ?
~$x^{2}$~
~$x^{2}+2$~
~$x^{2}+4$~
~$x^{2}+2x$~
~$x^{2}+4x$~
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(a-b)(a+b)=a2-b2
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(a-b)(a+b)=a2-b2