`^7C_7+^8C_7+^9C_7+^(10)C_7+^(20)C_7=` `^21 C_8` 2. `^21 C_(13)` 3. Neither 1 nor 2. 4. Both 1 and 2

.^(n) C_(2) + .^(7)C_(3) = .^(8) C_(3)

If ^(8)C_(r)-^(7)C_(3)^(7)C_(2)f in dr

The value of (.^(21)C_(1) - .^(10)C_(1)) + (.^(21)C_(2) - .^(10)C_(2)) + (.^(21)C_(3) - .^(10)C_(3)) + (.^(21)C_(4) - .^(10)C_(4)) + … + (.^(21)C_(10) - .^(10)C_(10)) is (A) 2^(21) - 2^(11) (B) 2^(21) - 2^(10) (C) 2^(20) - 2^(9) (D) 2^(20) - 2^(10)

^8C_(2)+^(8)C_(3)+^(8)C_(4)+...+^(8)C_(7) is equal to

Prove that .^(7)C_(2)+^(7)C_(3)=^(8)C_(3)

[(8 c_(1)+^(8)C_(3)+^(8)C_(5)+^(8)C_(7))]

If a^(3) = 1 + 7, 4^(2) = 1 + 5 + b , 5^(3) = 1 + 8 + c , then the value of a + b + c is