Question

-x²+4x=-5-16
Помогите решить ​

Answer 1

$-x^2+4x=-5-16\\-x^2+4x=-21\\-x^2+4x+21=0\\x^2-4x-21=0\\x^2+3x-7x-21=0\\x(x+3)-7(x+3)=0\\(x+3)(x-7)=0\\x+3=0,x-7=0\\x_{1}=-3,x_{2}=7$

Answer 2

Ответ:

-x²+4x=-5-16

$-x^{2} +4x=-5-16;\\\\-x^{2} +4x=-21;\\\\-x^{2} +4x+21=0;\\\\x^{2} -4x-21=0;\\\\a=1; b=-4; c=-21;\\\\D=b^{2} -4*a*c=(-4)^{2} -4*1*(-21)=16-(-84)=16+84=100\\\\\sqrt{D}= \sqrt{100} = 10\\\\x_{1} =\frac{-b+\sqrt{D} }{2a} =\frac{-(-4)+10}{2*1}=\frac{4+10}{2} =\frac{14}{2}=7\\\\x_{2} =\frac{-b-\sqrt{D} }{2a} =\frac{-(-4)-10}{2*1}= \frac{4-10}{2}=\frac{-6}{2}=-3$

Корни уравнения:

$x_{1} = 7 \\x_{2} =-3$