Find the sum: 9²+ 10²+11²+20².

Step-by-step explanation:

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d = a2 - a1 = 1

so common difference is 1

we have an =20

an = a+(n-1)d

(20) ^2 = 9^2+n-1

(20) ^2 =80 + n

400 - 80 =n

n = 320

sn = n\2(a+l)

= 160(81 + 400)

= 160(481)

= 76960

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the correct answer is $7.38

step-by-step explanation:

the answer is c: divide the arc's degree measure by 360°, then multiply by the circumference of the circle.