Consider the function y = acos(bx), where a > 0 and b > 0. Which change affects the locations of the x-intercepts of the graph?

The x-intercepts occur when a cos(bx) = 0. Since a is nonzero, this requires cos(bx) = 0, so bx = π/2 + kπ for an integer k and x = (π/2 + kπ)/b. Decreasing b changes these x-values, so it changes the intercept locations. Changing the sign of b does not, because cosine is an even function.

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