The only research method that can identify cause-and-effect relationships between variables is

Experiment type research method

Step-by-step explanation:

Experiment type research method - In this type of research method , researcher take one or two objective as variable and  done experiment on the basis of subject taken and analyze the outcome of experiment.

in this method different parameter can applied to the selected variable , to which cause and effect can be analyze. one demerits of this method is sampling method

part a

in a city ice cream is mostly only bought when the temperature is very high as ice cream cools down our

so we can derive the conclusion that as the temperature increases the number of ice creams sold also increases

part b

y intercept is 5

slope is 2

happy to

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answer:   x = 3 + √11     and     x = 3 - √11

step-by-step explanation:

x² - 6x + 9 = 11

(x - 3)² = 11

x - 3 = ±√11

    x = 3 ± √11

x = 3 + √11     and     x = 3 - √11