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Video: Yuav ua li cas koj pom lub vertex thiab Directrix?
2024 Tus sau: Miles Stephen | [email protected]. Kawg hloov kho: 2023-12-15 23:36
Tus qauv qauv yog (x - h)2 = 4p (y - k), qhov kev tsom xam yog (h, k + p) thiab cov directrix yog y = k-p. Yog hais tias tus parabola tig ces nws vertex yog (h, k) thiab nws axis ntawm symmetry yog parallel rau x-axis, nws muaj ib tug sib npaug ntawm (y - k)2 = 4p (x - h), qhov chaw tsom xam (h + p, k) thiab cov directrix yog x = h-p.
Ib yam li ntawd, koj yuav nrhiav tau daim ntawv vertex ntawm parabola li cas?
f (x) = a(x - h)2 + k, qhov twg (h, k) yog qhov vertex ntawm parabola . FYI: Cov phau ntawv sib txawv muaj kev txhais lus sib txawv ntawm kev siv "tus qauv daim ntawv Ib txhia hais tias f (x) = ax2 + bx + c yog "standard daim ntawv ", thaum lwm tus hais tias f (x) = a(x - h)2 +k yog "standard daim ntawv ".
Ib tug kuj yuav nug, ua li cas koj sau ib qho kev sib npaug rau parabola? Rau parabolas uas qhib qhov nce lossis nqis, daim ntawv qauv kev sib npaug yog (x - h)^2 = 4p(y - k). Rau parabolas uas qhib sideways, tus qauv daim ntawv kev sib npaug yog (y - k)^2 = 4p(x - h). Lub vertex los yog lub ntsis ntawm peb parabola yog muab los ntawm lub ntsiab lus (h, k).
Ib tug kuj yuav nug, ua li cas koj nrhiav tau lub vertex?
Cov kauj ruam los daws
- Tau qhov sib npaug hauv daim ntawv y = ax2 + bx + c.
- xam -b/2a. Qhov no yog x-coordinate ntawm lub vertex.
- Txhawm rau nrhiav y-coordinate ntawm lub vertex, tsuas yog ntsaws tus nqi ntawm -b / 2a rau hauv kab zauv rau x thiab daws rau y. Qhov no yog y-coordinate ntawm lub vertex.
Dab tsi yog P hauv parabola?
A parabola yog qhov sau los ntawm cov ntsiab lus hauv lub dav hlau uas sib npaug ntawm F thiab d. Qhov point F yog hu ua kev tsom xam thiab kab d hu ua directrix. Lub ntsiab lus P yog ib qho piv txwv ntawm qhov parabola yog li ntawd nws qhov kev ncua deb ntawm directrix, PQ, yog sib npaug rau nws qhov deb ntawm F, PF.
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