Sequences & Series
Arithmetic Progression (AP)
Grade 11
Question:
<p>If a,b,c are in AP, then (a - c)? equals</p>
HP
Arithmetic - Geometric Progression
4b? - ac
b? - 4ac
Step-by-Step Solution
Key Concept: Express everything in terms of first term and common difference. That converts a vague-looking progression problem into plain algebra.
Notice that this question is really about the first term and common difference. A clever move here is to parameterize the progression using those two quantities and translate every condition into algebra. Now, we invoke the power of the standard A.P. term and sum formulas, simplify step by step, and confirm the answer as $D$.
Correct Answer: 4