Question

а) х^2 + 4х - 21 = 0; б) 7х^2 - 4х - 3 = 0; в) 2х^2 - 2х - 1 = 0.

Answer 1

a)D=b^2-4ac=16-(-84)=100 k=$sqrt{100}$=10
x1=(-k+$sqrt{k^2-ac}$)/a=(-10+$sqrt{100+21}$)/1=-10+$sqrt{121}$=-10+11=1
x2=(-k$sqrt{k^2-ac}$)/a=(-10-$sqrt{100+21}$)/1=-10-$sqrt{121}$=-10-11=-21
b)D=16+84=100 k=10
x1=(-10+$sqrt{100+21}$)/7=(-10$sqrt{121}$)/7=(-10-11)/7=-3
x2=(-10-$sqrt{100+21}$)/7=(-10-$sqrt{121}$)/7=(-10+11)/7=1/7
c)D=4+8=12 k=$sqrt{12}$
 x1=$(-sqrt{12} - sqrt{ sqrt{12} +2} )/2=(-2 sqrt{3} - sqrt{2 sqrt{3} +2} )/2=(-2 sqrt{3} -$$sqrt{2( sqrt{3}+1 } ))/2$
x2=$(-sqrt{12} +sqrt{ sqrt{12} +2} )/2=(-2 sqrt{3} +sqrt{2 sqrt{3} +2} )/2=[tex](-2 sqrt{3} - sqrt{2( sqrt{3}+1 } ))/2$
/