đầu tiên phải tính x trước
x = \(\left(\sqrt{10}-\sqrt{6}\right).\sqrt{4+\sqrt{15}}\)
x= \(\sqrt{10}.\sqrt{4+\sqrt{15}}\)-\(\sqrt{6}.\sqrt{4+\sqrt{15}}\)
x= \(\sqrt{5}.\sqrt{8+2\sqrt{15}}\) - \(\sqrt{3}.\sqrt{8+2\sqrt{15}}\)
x= \(\sqrt{5}.\sqrt{3+2\sqrt{3}.\sqrt{5}+5}\) - \(\sqrt{3}.\sqrt{3+2\sqrt{3}.\sqrt{5}+5}\)
x= \(\sqrt{5}.\left(\sqrt{3}+\sqrt{5}\right)\) - \(\sqrt{3}.\left(\sqrt{3}+\sqrt{5}\right)\)
x = 5 + \(\sqrt{15}\) - 3 - \(\sqrt{15}\)
x = 2
thay vào M ta có:
M=\(\dfrac{\sqrt{4.2+4+\dfrac{1}{2}}}{\sqrt{2}.\left|2.2^2-2-1\right|}\)
M= \(\dfrac{\sqrt{\dfrac{25}{2}}}{\sqrt{2}.5}\)
M= \(\sqrt{\dfrac{25}{2}}\) . \(\dfrac{1}{\sqrt{2}.5}\)
M= \(\dfrac{1}{2}\)
