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Mark opens a savings account with an initial deposit of \$2000. He deposits \$35 each week. Elizabeth's savings account is represented by the function y = \$45x + \$2800, where y is the balance of Elizabeth's savings account after her initial deposit and a number of weekly deposits, x. Which statement BEST compares the rate of change for the two accounts?

Elizabeth deposited \$800 less than mark

Mark deposits \$10 more each week than Elizabeth.

Elizabeth deposits \$7 for every \$9 Mark deposits

Mark deposits \$10 less each week than Elizabeth

Mar 30, 2020

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y  =  ax + b     --->   the slope (a) represents the weekly deposit

the intercept (b) represents the initial deposit

Mark:         initial deposit = \$2000   weekly deposit = \$35      his equation:  y  =  35x + 2000

Elizabeth:  initial deposit = \$2800   weekly deposit = \$45      her equation:  y  =  45x + 2800

Elizabeth deposited \$800 more than Mark.

Mark deposits \$10 less each week than Elizabeth

Elizabeth deposits \$45 for every \$35 that Mark deposits; as a fraction, this is \$45/\$35  =  9/7, not 7/9

Mar 30, 2020