What are \( a \) and \( b \) when you write \( \sqrt{-16} \) in the form \( a+b i \), where \( a \) and \( b \) are real numbers?

24 Expresa com a identitats notables. \( \begin{array}{ll}\text { a) } 49 x^{2}-16 & \text { b) } 36 x^{2}-1 \\ \text { c) } x^{2}-18 x+81 & \text { d) } 121-100 x^{2} \\ \text { e) } 9 x^{2}+12 x+4 & \text { f) } 9 x^{2}-24 x+16 \\ \text { g) } 25-100 y^{2} & \text { h) } 4 x^{2}+16 x+16\end{array} \)

If \( x-6=0 \) is one of the solutions of the equation \( x+\frac{40}{x}=16 \), determine ONE value of \( y \) for which \( 2 y+3+\frac{40}{2 y+3}=16 \)

\( -\frac{1}{2 x}-\frac{1}{y}=-1 \) and \( \frac{1}{x}+\frac{1}{2 y}=8 \)

Qual è il grado di un polinomio se la funzione \( f(x) = 2x^4 - 3x^3 + x - 5 \)?

15. \( 5 x^{2}-47 x=156 \)