In which ones do i use elimination or substitution?

Compare these two waves: the blue and orange waves have the same pitch, but the blue wave is louder. the blue and orange waves have the same volume, but the blue wave has a higher pitch. the orange wave has a higher pitch, but the blue wave is louder. the blue wave has a higher pitch, but the orange wave is louder.

What happens to the area as the sliders are adjusted? what do you think the formula for the area of a triangle is divided by 2?

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)