X2-7x-44-x2-9=21
7x=74
x=74/7
x=10 4/7
100^k/(2*(2k-1))*(5^(2k-2))=
Sin20°+sin(90-77)sin57°-sin(90-57)sin77°=
sin20°+cos77°sin57°-cos57°sin77°=sin20°+sin57°*cos77°-cos57°*sin77°=sin20°+sin(57°-77°)=sin20°-sin20°=0
3x²-x+4=0
3x²+x-4=0
D=1-4*3(-4)=1+48=49=7²
x1=-1+7/6=1
x2=-1+7/6=-8/6=-4/3
ответ x1=1 x2=-4/3