SID (Sound Interface Device) was the name given to the Commodore 64's sound chip. It was one of the last sound chips to be made for any home computer prior to the digital sound revolution.
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<math>x^2+\frac{b}{a}x+\frac{b^2}{4a^2}=-\frac{c}{a}+\frac{b^2}{4a^2}.</math>
The left side is now a perfect square; it is the square of (x + ...