Question

1-2+3-4+.........s30=?

Answer 1

Hey dear,

◆ Answer -

1 - 2 + 3 - 4 + ... - 30 = -15

● Explaination -

Given sequence is -

S = 1 - 2 + 3 - 4 + ... -30

Let's divide this sequence into two APs for convenience -

S1 = 1 + 3 + 5 + ... + 29

S2 = -2 - 4 - 6 - ... - 30

For 1st AP, n = 15, a = 1, l = 29

S1 = n/2 (a + l)

S1 = 15/2 × (1+29)

S1 = 15/2 × 30

S1 = 225

For 2nd AP, n = 15, a = -2, l = -30

S2 = n/2 (a + l)

S2 = 15/2 × (-2-30)

S2 = 15/2 × (-32)

S2 = -240

Total sum is given by -

S = S1 + S2 = 225 - 240 = -15

Therefore,

1 - 2 + 3 - 4 + ... - 30 = -15

Best luck dear..

Answer 2

1 प्लस 2 प्लस 3 प्लस एच 30 इसका आंसर क्या है