Question

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Evaluate the following combinations. Write also your solutions.​

Answer 1

Answer:

Step-by-step explanation:

1. ⁷C₅ = ⁷C₂ = 7 x 6 / 2 = 21

2. ⁹C₈ = ⁹C₁ = 9

3. ¹²C₅ = 12 x 11 x 10 x 9 x 8 / 2 x 3 x 4 x 5

= 11 x 9 x 8 = 11 x 72 = 792

4. ²⁰C₁₇ = ²⁰C₃ = 20 x 19 x 18 / 2 x 3

= 19 x 3 = 57

5. ¹⁶C₁₃ = ¹⁶C₃ = 16 x 15 x 14 / 2 x 3

= 8 x 5 x 14 = 40 x 14 = 560

6. ⁷C₄ + ¹¹C₉ = ⁷C₃ + ¹¹C₂ = (7 x 6 x 5 / 2 x 3) + (11 x 10 / 2)

= 35 + 55 = 90

7. ⁷C₃ + ⁷C₄ + ⁷C₅ = 2(⁷C₃) + ⁷C₂ = (2 x 7 x 6 x 5 / 2 x 3) + (7 x 6 / 2)

= 70 + 21 = 91

Legit only this much I can do now.

Hope it is enough.