How does 170Q-20Q^2 = -20(Q-170/40)^2 ?

I am trying to figure out the 170/40

Is there a formula that you can show me to resolve future problems such as this

EXAMPLE: MICROCHIP MANUFACTURER 0 Sales are lots (of 100 chips) per week. Price per lot is in thousands of dollars. 0 Demand: Q=8.5-1120PP=170-20Q o Other factors than price that may impact demand are held fixed. They would affect the parameters. 0 Revenue: R = PXQ = (170-2OQ)Q = 170Q - 20Q2 = -20(Q - 170/40)2 + C, Q=17l4 is the optimal