Question

Выделите полный квадрат: 3х в квадрате-4х+5 х в квадрате-10+25 5х в квадрате-4х+3 х в квадрате-12+36 3х в квадрате-8+5 х в квадрате-16+64

Answer 1

$3x^2-4x+5=(\sqrt{3}x)^2-2\cdot\sqrt{3}x\cdot\frac{2}{\sqrt{3}}+(\frac{2}{\sqrt{3}})^2-(\frac{2}{\sqrt{3}})^2+5 =\\= (\sqrt{3}x-\frac{2}{\sqrt{3}})^2-\frac{4}{3}+5=\frac{1}{3}(3x-2)^2+3\frac{2}{3};$

$x^2-10x+25=x^2-2\cdot x\cdot5+5^2=(x-5)^2;$

$5x^2-4x+3=(\sqrt{5}x)^2-2\cdot\sqrt{5}x\cdot\frac{2}{\sqrt{5}}+(\frac{2}{\sqrt{5}} )^2-(\frac{2}{\sqrt{5}})^2+3 =\\= (\sqrt{5}x-\frac{2}{\sqrt{5}})^2-\frac{4}{5}+3 = \frac{1}{5}(5x-2)^2+2\frac{1}{5},$

$x^2-12x+36=x^2-2\cdot x\cdot6+6^2=(x-6)^2$

$3x^2-8x+5=3(x^2-\frac{8}{3}x)+5=3(x^2-2\cdot x\cdot\frac{4}{3}+(\frac{4}{3})^2-(\frac{4}{3})^2)+5 =\\= 3(x-\frac{4}{3})^2-3\cdot\frac{16}{9}+5= 3(x-\frac{4}{3})^2-\frac{16}{3}+5= 3(x-\frac{4}{3})^2-\frac{1}{3} =\\= \frac{1}{3}(3x-4)^2- \frac{1}{3} ;$

$x^2-16x+64=(x-8)^2$