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The number of solutions of the equation \(x_1 + x_2 + x_3 + x_4 = 50\), where \(x_1, x_2, x_3, x_4\) are integers with \(x_1 \geq 1, x_2 \geq 2, x_3 \geq 0, x_4 \geq 0\) is

Question and options

The number of solutions of the equation x1+x2+x3+x4=50x_1 + x_2 + x_3 + x_4 = 50, where x1,x2,x3,x4x_1, x_2, x_3, x_4 are integers with x1≥1,x2≥2,x3≥0,x4≥0x_1 \geq 1, x_2 \geq 2, x_3 \geq 0, x_4 \geq 0 is
  1. 20200
  2. 19200
  3. 19600
  4. 18400

Answer and explanation

Correct answer: C - 19600
Put y1=x1-1, y2=x2-2: y1+y2+x3+x4=47 with all >=0, count C(50,3)=19600.

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