Yuav ua li cas koj pom lub vertex ntawm kab rov tav parabola?
Yuav ua li cas koj pom lub vertex ntawm kab rov tav parabola?

Video: Yuav ua li cas koj pom lub vertex ntawm kab rov tav parabola?

Video: Yuav ua li cas koj pom lub vertex ntawm kab rov tav parabola?
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Yog ib parabola muaj ib kab rov tav axis, tus qauv daim ntawv ntawm kev sib npaug ntawm cov parabola yog qhov no: (y -k)2 = 4p(x - h), where p≠ 0. The vertex ntawm no parabola yog ntawm (h, k). Kev tsom xam yog nyob ntawm (h + p, k). Thedirectrix yog kab x = h - p.

Yog li ntawd, ua li cas koj thiaj nrhiav tau lub vertex thiab directrix ntawm parabola?

Tus qauv qauv yog (x - h)2 = 4p (y - k), qhov twg tsom yog (h, k + p) thiab cov directrix yog y=k-p. Yog tias parabola yog tig kom nws vertex yog (h, k) thiab nws axis ntawm symmetry yog parallel rau thex-axis, nws muaj kev sib npaug ntawm (y - k)2 = 4p (x -h), qhov twg tsom yog (h + p, k) thiab cov directrix yog x = h-p.

Tsis tas li ntawd, qhov sib npaug ntawm ib sab parabola yog dab tsi? Daim ntawv "General" ntawm a parabola kev sib npaug yog tus uas koj tau siv, y = ax2 + bx + c - tshwj tsis yog lub quadratic yog " sab xis ", hauv qhov xwm txheej no kev sib npaug yuav zoo ib yam li x = ay2 + los ntawm +c.

Yog li ntawd, koj yuav nrhiav tau qhov vertex ntawm parabola sib npaug li cas?

Qhov no point, qhov twg cov parabola hloov cov kev taw qhia, hu ua " vertex ". Yog hais tias lub quadratic sau nyob rau hauv daim ntawv y = a(x – h)2 + k, tom qab ntawd vertex yog qhov point (h, k). Qhov no ua rau kev nkag siab, yog tias koj xav txog nws. Thesquared feem yog ib txwm zoo (rau sab xis-up parabola ), tshwj tsis yog nws yog xoom.

Tus nqi ntawm p yog qhov vertex ntawm parabola?

Qhov tseeb nqi p yog qhov kev ncua deb ntawm cov vertex thiab qhov tsom xam thiab qhov nrug ntawm qhov vertex thiab directrix. (Qhov kos npe rau p qhia kuv txoj kev twg parabola ntsej muag.) Txij li thaum lub tsom thiab directrixare ob chav nyob sib nrug, ces qhov kev ncua deb no yuav tsum yog ib chav tsev, yog li | p | = 1.

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