Question

Найдите корни уравнения: а)x^2/4=2x-3 б)x^2/3=5x-12 в)x^2+1/5=2x-4 г)x^2-1/2=6x-18

Answer 1

$1) \frac{x^2}{4} = 2x-3 \\ \\ x^2=4(2x-3) \\ x^2=8x-12 \\ x^2-8x+12=0 \\ D=b^2-4ac=64-48=16 \\ \sqrt{D} =4 \\ x_{1}= \frac{8+4}{2}=6 \\ x_{2} = \frac{8-4}{2}=2 \\ \\ 2) \frac{x^2}{3}=5x-12 \\ \\ x^2=3(5x-12) \\ x^2=15x-36 \\ x^2-15x+36=0 \\ D=b^2-4ac=225-144= 81 \\ \sqrt{D} =9 \\ x_{1}= \frac{15+9}{2} =12 \\ x_{2}= \frac{15-9}{2}=3 \\ \\ 3) \frac{x^2+1}{5}=2x-4 \\ \\ x^2+1=5(2x-4) \\ x^2+1=10x-20 \\ x^2-10x+21=0 \\ D=b^2-4ac=100-84=16 \\ \sqrt{D}=4 \\ x_{1}= \frac{10+4}{2}=7 \\$ $x_{2}= \frac{10-4}{2} =3 \\ \\ 4) \frac{x^2-1}{2} =6x-18 \\ x^2-1=2(6x-18) \\ x^2-1=12x-36 \\ x^2-12x+35=0 \\ D=b^2-4ac=144-140=4 \\ \sqrt{D}=2 \\ x_1= \frac{12+4}{2}=8 \\ \\ x_2= \frac{12-4}{2} = 4$