Question

x² + 7x - 18 = 0 помогите пж срочно оч сррчно​

Answer 1

Ответ:

$x^{2} +7x-18=0;\\\\a=1; b=7; c=-18;\\\\D=b^{2} -4*a*c=7^{2}-4*1*(-18)=49-(-72)=49+ 72=121\\\\\sqrt{D} =\sqrt{121}=11;\\\\x_{1} =\frac{-b+\sqrt{D} }{2*a} =\frac{-7+11}{2*1}= \frac{4}{2} =2\\\\x_{2} =\frac{-b-\sqrt{D} }{2*a} =\frac{-7-11}{2*1}=\frac{-18}{2}=-9 \\\\ x_{1}=2;x_{2}=-9.$