Letf:X->[- infinity, infinity] be an extended real-valued function defined on a

measure space (X, F, m) . Prove that {x:f(x) > -infinity}

is in segma-algebra F ,and {x: - infinity< f(x)< infinity}

is in segma-algebra F

how can I apply the definition of an extended real-valued function to prove this, any help would be appraciated.

Thanks,