Question

find the sum of the series: 2+7+12+...........297.

Answer 1

Hey here is your answer
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$s = \frac{n}{2} (a + l)$
here,
a = 2
l = 297
d = 5
n = ?

T$= (a + (n - 1)d)$
$297 = 2 + (n - 1)5 \\ 297 - 2 = (n - 1)5 \\ \frac{295}{5} = (n - 1) \\ 59 + 1 = n \\ n = 60$
now , sum of given ap
$s = \frac{60}{2} (2 + 297) \\ \: \: \: = 30 \times 299 \\ \: \: \: =8970$
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Hope it may helpful to you
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Answer 2

Step-by-step explanation:

(2x−3y+5z)(4x

2

+9y

2

+25z

2

+6xy+15z−10xz)

=(2x−3y+5z)[(2x)

2

+(3y)

2

+(5z)

2

−(2x)(−3y)−(−3y)(5z)−(2x)(5z)]

Using formula (x+y+z)(x

2

+y

2

+z

2

−xy−yz−zx)=x

3

+y

3

+z

3

−3xyz

=(2x)

3

+(−3y)

3

+(5z)

3

−3.2x.(−3y).5z

=(2x)

3

+(−3y)

3

+(5z)

3

+90xyz