a^2-a-1=0 eching

$$a ^ { 2 } - a - 1 = 0$$

a uchun yechish

$$a = \frac{\sqrt{5} + 1}{2} \approx 1,618033989$$

$$a=\frac{1-\sqrt{5}}{2}\approx -0,618033989$$

Kvadrat tenglamalaridan foydalanish qoidalari

ax^{2}+bx+c=0 shaklidagi barcha tenglamalarni kvadrat formulasi bilan yechish mumkin: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. Kvadrat formula ikki yechmni taqdim qiladi, biri ± qo'shish bo'lganda, va ikkinchisi ayiruv bo'lganda.

$$a^{2}-a-1=0$$

Ushbu tenglama standart shaklidadir: ax^{2}+bx+c=0. Kvadrat tenglama formulasida, \frac{-b±\sqrt{b^{2}-4ac}}{2a} 1 ni a, -1 ni b va -1 ni c bilan almashtiring.

$$a=\frac{-\left(-1\right)±\sqrt{1-4\left(-1\right)}}{2}$$

-4 ni -1 marotabaga ko'paytirish.

$$a=\frac{-\left(-1\right)±\sqrt{1+4}}{2}$$

1 ni 4 ga qo'shish.

$$a=\frac{-\left(-1\right)±\sqrt{5}}{2}$$

-1 ning teskarisi 1 ga teng.

$$a=\frac{1±\sqrt{5}}{2}$$

a=\frac{1±\sqrt{5}}{2} tenglamasini yeching, bunda ± musbat. 1 ni \sqrt{5} ga qo'shish.

$$a=\frac{\sqrt{5}+1}{2}$$

a=\frac{1±\sqrt{5}}{2} tenglamasini yeching, bunda ± manfiy. 1 dan \sqrt{5} ni ayirish.

$$a=\frac{1-\sqrt{5}}{2}$$

Tenglama yechildi.

$$a=\frac{\sqrt{5}+1}{2} a=\frac{1-\sqrt{5}}{2}$$

Kvadratni yakunlash bo'yicha qadamlar

Bu kabi kvadrat tenglamalarni kvadratni yakunlab yechish mumkin. Kvadratni yechish uchun tenglama avval ushbu shaklda bo'lishi shart: x^{2}+bx=c.

$$a^{2}-a-1=0$$

1 ni tenglamaning ikkala tarafiga qo'shish.

$$a^{2}-a-1-\left(-1\right)=-\left(-1\right)$$

O‘zidan -1 ayirilsa 0 qoladi.

$$a^{2}-a=-\left(-1\right)$$

0 dan -1 ni ayirish.

$$a^{2}-a=1$$

-1 ni bo‘lish, x shartining koeffitsienti, 2 ga -\frac{1}{2} olish uchun. Keyin, -\frac{1}{2} ning kvadratini tenglamaning ikkala tarafiga qo‘shing. Ushbu qadam tenglamaning chap qismini mukammal kvadrat sifatida hosil qiladi.

$$a^{2}-a+\left(-\frac{1}{2}\right)^{2}=1+\left(-\frac{1}{2}\right)^{2}$$

Kasrning ham suratini, ham maxrajini kvadratga ko'paytirib -\frac{1}{2} kvadratini chiqarish.

$$a^{2}-a+\frac{1}{4}=1+\frac{1}{4}$$

1 ni \frac{1}{4} ga qo'shish.

$$a^{2}-a+\frac{1}{4}=\frac{5}{4}$$

a^{2}-a+\frac{1}{4} omili. Odatda, x^{2}+bx+c mukammal kvadrat bo'lsa, u doimo \left(x+\frac{b}{2}\right)^{2} omil sifatida bo'lishi mumkin.

$$\left(a-\frac{1}{2}\right)^{2}=\frac{5}{4}$$

Tenglamaning ikkala tarafining kvadrat ildizini chiqarish.

$$\sqrt{\left(a-\frac{1}{2}\right)^{2}}=\sqrt{\frac{5}{4}}$$

Qisqartirish.

$$a-\frac{1}{2}=\frac{\sqrt{5}}{2} a-\frac{1}{2}=-\frac{\sqrt{5}}{2}$$

\frac{1}{2} ni tenglamaning ikkala tarafiga qo'shish.

$$a=\frac{\sqrt{5}+1}{2} a=\frac{1-\sqrt{5}}{2}$$