3x+6x+9x .................... to n terms = 3/2n(n+1)x

**3x + 6x + 9x + ......n terms**

they are in AP

therefore, the common difference is 3x

sum = n/2 [2.3x + (n - 1) 3x]

=3*n (2 + n - 1)/2

=3/2 nx (1 + n)

Hence proved !

3x+6x+9x .................... to n terms = 3/2n(n+1)x

they are in AP

therefore, the common difference is 3x

sum = n/2 [2.3x + (n - 1) 3x]

=3*n (2 + n - 1)/2

=3/2 nx (1 + n)

Hence proved !

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