3x^2-21=0 eching

$$3 x ^ { 2 } - 21 = 0$$

x uchun yechish

$$x=\sqrt{7}\approx 2,645751311$$

$$x=-\sqrt{7}\approx -2,645751311$$

Kvadrat ildizini topish bo'yicha qadamlar

21 ni ikki tarafga qo’shing. Har qanday songa nolni qo‘shsangiz, o‘zi chiqadi.

$$3x^{2}=21$$

Ikki tarafini 3 ga bo‘ling.

$$x^{2}=\frac{21}{3}$$

7 ni olish uchun 21 ni 3 ga bo‘ling.

$$x^{2}=7$$

Tenglamaning ikkala tarafining kvadrat ildizini chiqarish.

$$x=\sqrt{7} x=-\sqrt{7}$$

Kvadrat tenglamalaridan foydalanish qoidalari

Bu kabi kvadrat tenglamalarni x^{2} sharti bilan, biroq x shartisiz hamon kvadrat tenglamasidan foydalanib yechish mumkin, \frac{-b±\sqrt{b^{2}-4ac}}{2a}, ular standart formulaga solingandan so'ng: ax^{2}+bx+c=0.

$$3x^{2}-21=0$$

Ushbu tenglama standart shaklidadir: ax^{2}+bx+c=0. Kvadrat tenglama formulasida, \frac{-b±\sqrt{b^{2}-4ac}}{2a} 3 ni a, 0 ni b va -21 ni c bilan almashtiring.

$$x=\frac{0±\sqrt{0^{2}-4\times 3\left(-21\right)}}{2\times 3}$$

0 kvadratini chiqarish.

$$x=\frac{0±\sqrt{-4\times 3\left(-21\right)}}{2\times 3}$$

-4 ni 3 marotabaga ko'paytirish.

$$x=\frac{0±\sqrt{-12\left(-21\right)}}{2\times 3}$$

-12 ni -21 marotabaga ko'paytirish.

$$x=\frac{0±\sqrt{252}}{2\times 3}$$

252 ning kvadrat ildizini chiqarish.

$$x=\frac{0±6\sqrt{7}}{2\times 3}$$

2 ni 3 marotabaga ko'paytirish.

$$x=\frac{0±6\sqrt{7}}{6}$$

x=\frac{0±6\sqrt{7}}{6} tenglamasini yeching, bunda ± musbat.

$$x=\sqrt{7}$$

x=\frac{0±6\sqrt{7}}{6} tenglamasini yeching, bunda ± manfiy.

$$x=-\sqrt{7}$$

Tenglama yechildi.

$$x=\sqrt{7} x=-\sqrt{7}$$