The first term of an arithmetic progression is and the common difference is . Find the sum of the first terms.
Answer and explanation
Correct answer: C.
- Step 1: Use . Step 2. . **Answer: . Why not the others:** is what you get if you use in place of . is what you get if you forget to halve. is what you get if you put instead of in the formula.
Practise more Matrices, calculus and coordinate geometry.
Free questions with an explanation for every one, and full timed WBJEE mock tests.
More Matrices, calculus and coordinate geometry questions
- Find the determinant of the 3×3 matrix with rows (-2, 0, 3); (-1, 5, -1); (2, 1, -1).
- If A has rows (3, -3) and (3, -1) and B has rows (-3, 4) and (3, 2), find the entry in row 2, column 1 of AB.
- Find the coordinates of the focus of the parabola y² = 12x.
- Find a × b for a = 3i + 4j − 1k and b = 2i − 2j + 3k.
- Solve dy/dx = 2x with y(0) = -1. What is y(3)?
- How many permutations of 10 objects taken 3 at a time are there?