Find the value of the polynomial $5x - 4x^2 + 3$ at $x = -1$.

Without actually calculating the cubes,find the value of each of the following: $(28)^{3} + (-15)^{3} + (-13)^{3}$

Evaluate the following product without multiplying directly: $104 \times 96$

Check whether the polynomial $q(t) = 4t^3 + 4t^2 - t - 1$ is a multiple of $2t + 1$.

Factorise: $49 a^{2}+70 a b+25 b^{2}$

Which of the following expressions are polynomials in one variable and which are not? State reasons for your answer: $y + \frac{2}{y}$