rosypetals
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- Dec 28, 2020
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If you prefer, you can write an equation for [MATH]a_{21}[/MATH] in terms of [MATH]a_1[/MATH] and [MATH]d[/MATH], and then solve for [MATH]a_1[/MATH].Which of the following is true regarding the image shown.
View attachment 24052
This is a problem of arithmetic progression.
...after subtracting twenty-one 2s?Here's another way to consider, for students who have a good understanding of arithmetic sequences.
The given information tells us that we get 18, after subtracting twenty-one 2s from the number a1.
So, how much did we subtract from a1 altogether? In other words:
a1 - (total amount subtracted) = 18
?
Thanks for catching my careless typo. (My hands need a better understanding of APs, ha.)… subtracting twenty-one 2s?