If one root of 5x² + 26x + k = 0 is reciprocal of the other, then what is the value of k?

In how many ways can a team of 5 players be selected from 8 players so as not to include a particular player?

What is the coefficient of the middle term in the expansion of (1 + 4x + 4x²)⁵?

If $\rm tan\:x=-\dfrac{3}{4}$ and x is in the second quadrant, then what is the value of sin x ⋅ cos x?