Determine the mean and variance of the random variable with the following probability mass function. f left-parenthesis x right-parenthesis equals left-parenthesis 8divided by 9right-parenthesis left-parenthesis 1 divided by 9right-parenthesis Superscript x Baseline comma x equals Number 0 , 1 , 2 , . . . Hint: Use the formula for the sum of the infinite series where .

Use the following statements to write a compound statement for the conjunction or disjunction. then find its truth value. p: an isosceles triangle has two congruent sides. q: a right angle measures 90° r: four points are always coplanar. s: a decagon has 12 sides. a) a right angle measures 90° or an isosceles triangle has two congruent sides; true. b) a right angle measures 90° and an isosceles triangle has two congruent sides; true. c) a right angle measures 90° and an isosceles triangle does not have two congruent sides; false. d) a right angle measures 90° or an isosceles triangle does not have two congruent sides; true.