Given Sn=2n^2 - 5n, find (a) first term
(b) 9th term
(c) sum of the terms from the 4th term to the 8th term

a) -3

b) 117

c) 100

Step-by-step explanation:

(a) 2(1)²-5(1)

1²= 1

2×1= 2

2-5= -3

(b) 2(9)²-5(9)

9²= 81

81×2= 162

162-45= 117

(c) 2(4)²-5(4) +2(8)²-5(4)

4²=16

16×2= 32

32-20= 12

8²=64

64×2= 128

128-40= 88

88+12= 100

hope it helps!

answer:

payment just for service  

→

$

87.12

payment for service including tax

→

$

94.09

explanation:

service only with 20% tip  

→

$

72.6

(

1

+

20

100

)

=

$

87.12

in the opening of the question the word 'service' is associated only with the pretax value.

the closing part of the question asks: how much did she pay for the  

service

−−−−−−  

so technically the answer is  

→

$

72.6

(

1

+

20

100

)

=

$

87.12

however, the intention of the question provider may have been that your answer is to be  

$

87.12

(

1

+

8

100

)

=

$

94.09

to 2 decimal places.

'

payment just for service  

→

$

87.12

payment for service including tax

→

$

94.09

tony b

mar 21, 2017

answer:

trying to explain it another way

explanation:

service charge  

.

→

$

72.60

20% tip  

20

100

×

$

72.60

=

$

14.52

−−−−−−  

←

add

$

87.12

tax  

8

100

×

$

87.12

=

$

6.97

−−−−−  

←

add

$

94.09

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