Final answer:
To find the derivative of the function y = x² - 9x², use the power rule for derivatives.
Step-by-step explanation:
To find the derivative of the function y = x² - 9x², we need to use the power rule for derivatives. The power rule states that the derivative of x^n is n*x^(n-1). Applying this rule, we can find the derivative of x² as 2x and the derivative of 9x² as 18x. So the derivative of y = x² - 9x² is dy/dx = 2x - 18x = -16x.