Just remember the form: y² = 4ax. Here, 4a = 12, so a = 3. Then focus is (a,0) = (3,0), directrix is x = -a so x = -3, and latus rectum length is 4a = 12.
I practice this fast because between fixing mobiles, I scribble formulas on my son’s old tuition receipts.
Frankly, the "obvious" advice is to visualize the graph, but under time pressure, you just drill it until it’s as automatic as adjusting the focus on my old camera.
#exams#study
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