Question

на фото 4 примера напишите подробно

Answer 1

$1)\\ 0,07x^2-50=2,1x-50\\ 0,07x^2=2,1x\\ \frac{7}{100}x^2=\frac{21}{10}x\\ x^2=30x = x^2-30x=0\\ x(x-30)=0\\\\ \left \{ {{x=0} \atop {x-30=0}} \right. \left \{ {{x_{1} =0} \atop {x_{2} =30}} \right. \\\\ 2)\\ -0,5x^2+\sqrt{5} x=0\\ -\frac{1}{2} x^2+\sqrt{5} x=0\\ -x^2+2\sqrt{5} x=0\\ -x(x-2\sqrt{5} )=0 | *(-1)\\ x(x-2\sqrt{5} )=0\\\\ \left \{ {{x=0} \atop {x-2\sqrt{5}}=0} \right. \left \{ {{x_{1}=0} \atop {x_{2} =2\sqrt{5} }} \right. \\\\$

$3)\\ 9x^2-10x=7x^2-15x=0\\ 9x^2-10x-7x^2+15x\\ 2x^2+5x=0\\ x(2x+5)=0\\ \left \{ {{x=0} \atop {2x+5=0}} \right. \left \{ {{x_{1} =0} \atop {x_{2} =-2,5}} \right. \\ \\ 4)\\ \frac{2}{3} x^2=5x\\ 2x^2=15x\\ 2x^2-15x=0\\ x(2x-15)=0\\ \left \{ {{x=0} \atop {2x-15=0}} \right. \left \{ {{x_{1}=0 } \atop {x_{2}=7,5}} \right.$