tìm x để biểu thức sau có nghĩa
a,\(\sqrt{-7x}\)
b,\(\sqrt{8-x}\)
c,\(\sqrt{3x+11}\)
d, \(\sqrt{\dfrac{2x}{5}}\)
e, \(\sqrt{-7x+5}\)
f,\(\sqrt{\dfrac{1}{-2+x}}\)
g,\(\sqrt{2+x^2}\)
h,\(\sqrt{x+7}.\sqrt{x-8}\)
i, \(\sqrt{\left(x+2\right).\left(x-3\right)}\)
k, \(\sqrt{\dfrac{x+5}{3-x}}\)