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QJEEM24Ma1a63: JEE Main 2024 Mathematics - Class 11 JEEM24Ma1a63 Solution: If the set has elements and ∑ n = 1 m ( 1 − i n ! ) = x + i y , …

If the set R={(a,b):a+5b=42,a,b∈N}R=\{(a, b): a+5 b=42, a, b \in \mathbb{N}\} has mm elements and ∑n=1m(1−in!)=x+iy, where i=−1i=\sqrt{-1} , then the value of m+x+ym+x+y is

Multiple Choice Options

  • A 12
  • B 4
  • C 8
  • D 5

Step-by-Step Verified Solution

R={(a,b):a+5b=42}R=\{(a, b): a+5 b=42\}

Then R={(2,8),(7,7),(12,6),(17,5),(22,4),(27,3),(32,2),(37,1)}R=\{(2,8),(7,7),(12,6),(17,5),(22,4),(27, 3),(32,2),(37,1)\}

amp; and ∑n=1m=8(1−in!)=x+iyamp;∴∑n=18(1−in!)=8−(i+i2+i6+1+1+1+1+1)amp;=5−iamp;∴x=5,y=−1amp;x+y+m=5−1+8=12\begin{aligned}& \text { and } \sum_{n=1}^{\substack{m=8}}\left(1-i^{n!}\right)=x+i y \\& \therefore \sum_{n=1}^8\left(1-i^{n!}\right)=8-\left(i+i^2+i^6+1+1+1+1+1\right) \\& =5-i \\& \therefore x=5, y=-1 \\& x+y+m=5-1+8=12\end{aligned}

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