How would you write the explanation

Which of the following parabolas opens down?

Ahypothesis is: a the average squared deviations about the mean of a distribution of values b) an empirically testable statement that is an unproven supposition developed in order to explain phenomena a statement that asserts the status quo; that is, any change from what has been c) thought to be true is due to random sampling order da statement that is the opposite of the null hypothesis e) the error made by rejecting the null hypothesis when it is true

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?