Explanation

\(^9C_x = 4[^7C_{x - 1}]\)

\(\frac{9!}{x!(9 - x)!}=4*\frac{7!}{(x - 1)!(7 - (x - 1)!)}\)

\(\frac{9!}{x!(9 - x)!} = 4*\frac{7!}{(x - 1)!(8 - x)!}\)

\(=\frac{9 \times 8 \times 7!}{x(x - 1)!(9 - x)(8 - x)!}=4*\frac{7!}{(x - 1)!(8 - x)!}\)

Cancel out the common terms

\(=\frac{9 \times 8}{x(9 - x)}=\frac{4}{1}\)

\(=4x(9-x) = 9*8\)

\(=36x- 4x^2=72\)

divide thru by 4

\(=x^2 - 9x+18 = 0\)

\(=x^2-6x-3x+18=0\)

\(=x(x-6)-3(x-6)=0\)

\(=(x-6)(x-3)=0\)

\(\therefore x\) = 6 or 3

• whats is the difference between phrase and clause? Answer this

  1 Answers   ·   English Language   ·   2 days ago
• poetry differs from prose by its use of ...... a)song b)rhythms c)flat character d)condenced language? Answer this

  2 Answers   ·   Literature in English   ·   2 days ago
• Which of the following physical properties belongs to hydrogen sulphide gas? A) Colorless with a pleasant fruity smell B) Greenish-yellow... Answer this

  1 Answers   ·   Chemistry   ·   2 days ago