Question

The value of (1³ +2³ +3³ + ... +15³) - (1+2+3+...+15) = ...... is :​

Answer 1

Answer: 14280

Step-by-step explanation:

We have to find 1³ + 2³ + 3³....... 15³

Hence, let n = 15.

Therefore, [n² × (n+1)²]/4

:. [15² × (16)²]/4

[225 × 256]/4

57600/4

14400

Then we have to find 1 + 2 + 3...... 15

Hence let n again be 15.

Therefore, n(n+1)/2

:. 15 × 16/2

240/2

120

So, 14400 - 120 = 14280

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