<s>[INST] Help simplify using quadratic formula $\dfrac{4\pm\sqrt{28}}{2}=2\pm\sqrt7$
My Question is how did $\dfrac{4\pm\sqrt{28}}{2}$ become simplified as $2\pm\sqrt7$
Can you help me by explaining the steps clearly 
:) Many Thanks
 [/INST] Notice that $\sqrt{28}=\sqrt{4\times7}=\sqrt{4}\times\sqrt{7}=2\sqrt{7}$.
Hence $\dfrac{4\pm\sqrt{28}}{2}=\dfrac{4\pm2\sqrt{7}}{2}=\dfrac{2(2\pm\sqrt{7})}{2}=2\pm\sqrt{7}$.
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