Help meee I don’t understand

Volume of cylinder with a radius of 8cm and height of 25 cm

Find the zero function by factoring (try to show work) h(x)=-x^2-6x-9

Acompany that manufactures and sells guitars made changes in their product range. from the start they had 20 models. then they reduced the number of models to 15. as a result, the company enjoyed a 10% increase in turnover. - how much did the stock level change? in (%)