Question

Need help please will give brainliest answer!

Answer 1

Answer:

lower limit is n=1

upper limit is n=18

n=1 to 18∑(7n-4)

Number of beads = 1125

Step-by-step explanation:

Given series is 3+10+17+24.....

we find the formula to find nth term(explicit formula)

first term (a1) = 3

common difference (d)= 7

$a_n = a_1+(n-1)d$

$a_n = 3+(n-1)7$

$a_n = 3+7n-7$

$a_n =7n-4$

total of 18 rows

So we find sum for n =1  to 18

lower limit is n=1

upper limit is n=18

n=1 to 18∑(7n-4)

(b) to find total number of beads we apply sum formula

$s_n = \frac{n}{2}(2a+(n-1)d)$

n=18, a=3, d= 7

$s = \frac{18}{2}(2(3)+(18-1)7)$

S= 9(125)=1125

Number of beads = 1125