Question:hard

The line \(y = 2x+c\) passes through a point that is equidistant from both the axes and lies in the first quadrant \((x > 0,y > 0)\). Then the value of c is...

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The 7 identical balls count as one kind; select any number of them and fill the rest from 16 distinct balls.
Updated On: Oct 1, 2026
  • \(0\)
  • \(1\)
  • \(2\)
  • \(-2\)
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The Correct Option is D

Solution and Explanation

Step 1: Generating function:
The count is the coefficient of $x^{12}$ in $(1 + x + \dots + x^7)(1 + x)^{16}$, because the identical balls give a factor $1 + x + \dots + x^7$ and the distinct balls give $(1 + x)^{16}$.

Step 2: Evaluate:
Collecting the coefficient of $x^{12}$ gives ${}^{16}C_{12} + {}^{16}C_{11} + \dots + {}^{16}C_{5} = 62322$.
Checking the options numerically, ${}^{18}C_6 + {}^{18}C_8 = 18564 + 43758 = 62322$. So (A) is correct.

Final Answer:
62322 ways, option (A). \[ \boxed{{}^{18}C_6 + {}^{18}C_8} \]
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