What is the sum of the coefficients of $(x^2 - x - 1)^{99}$?

If the roots of $x^5-ax^4+bx^3-cx^2+dx-1=0$ are all positive such that their arithmetic mean and geometric mean are equal,then $a+b+c+d=$

Find the value of $\frac{18^3 + 7^3 + 3 \times 18 \times 7 \times 25}{3^6 + 6 \times 243 \times 2 + 15 \times 81 \times 4 + 20 \times 27 \times 8 + 15 \times 9 \times 16 + 6 \times 3 \times 32 + 64}$

The sum of the coefficients in the expansion of $(1+x+x^2)^n$ is

Let $n \geq 5$ be an integer. If $9^{n}-8n-1=64\alpha$ and $6^{n}-5n-1=25\beta$,then $\alpha-\beta$ is equal to

The number of terms in the expansion of $(a + b + c)^n$ will be