Phan tích da thức thanh nhan tu x*x-21*x+10

x.x-21x+10

=x²-21x+10

=(x²-2.x.21/2+441/4)-401/4

=(x-21/2)²-401/4

=(x-21/2 -√401/2)(x-21/2 +√401/2)

=(x+(-21+√401)/2)(x+(-21+√401)/2))