b, x10 + x5 + 1
= x10 - x + x5 - x2 + x2 + x + 1
= x(x9 - 1) + x2(x3 -1) + (x2 + x + 1)
= x(x3 - 1)(x6 + x3 + 1) + x2(x - 1)(x2 + x + 1) + (x2 + x + 1)
= x(x - 1)(x2 + x + 1)(x6 + x3 + 1) + x2(x2 + x + 1) + (x2 + x + 1)
= (x2 + x + 1)[x(x6 + x3 + 1) + x2 + 1]
câu a không biết làm :v
a) x4 + 3x2 + 4
= x4 + 4x2 + 4 - x2
= ( x2 + 2 )2 -x2
= ( x2 + 2 + x ) . (x2 + 2 - x )
b) x10 + x5 + 1
= x10 + x5 + x2 - x2 + x - x +1
= ( x10 - x ) + ( x5 - x2 ) + ( x2 + x +1 )
= x . ( x9 - 1 ) + x2. ( x3 - 1) + ( x2 + x +1 )
= x. ( x3-1).(x3+1) + x2. (x3 - 1) + ( x2 + x +1 )
= ( x3 - 1). [x. ( x3 + 1 ) + x2 ] + ( x2 + x +1)
bạn phân tích ( x3 - 1) ra để có ( x2 + x +1) chung rr tiếp tục gộp lại nha
a) x4 + 3x2 + 4
= ( x2 )2 + 4x2 + 22 - x2
= [(x2)2 + 2(2)(x2) + 2] - x2
= (x2 + 2)2 - x2
= ( x2 + 2 + x)( x2 + 2 - x)
b) x10 + x5 +1
= ( x10 - x) +( x5- x2) +( x2 + x + 1)
= x.[(x3)3 - 1] + x2.(x3 - 1) + (x2 + x +1)
= x.( x3 - 1).( x6 + x3 1) + x2.(x3 - 1) + ( x2 + x +1 )
= (x2 +x +1).[x.(x-1).( x6+ x3 +1) + x2 +1]