13. Which equation represents y = x2 - 10x + 30 in vertex form? y = (x - 5)2 + 5
y = (x – 5)2 + 55
y = (x – 5)2 - 5
y = (x - 5)2 + 30

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 (%)