Elite marathon race times improved from 5 to ~20 years, remained linear between ~20 and ~35 years, and started to increase at the age of ~35 years in a curvilinear manner with increasing age in both women and men. The sex difference in elite marathon race time increased non-linearly and was lowest at the age of ~49 years.
Be more specific on the first one
Answer:
0
Step-by-step explanation:

Changing x to y and y to x:

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Answer:
umm check your math book in page 445
Step-by-step explanation: