Question

1. Cho :

A(x) = 5x⁴ - 5 + 6x³ +x⁴ - 5x -12

B(x) = 8x⁴ +2x³ - 2x⁴ + 4x³ - 5x - 15 - 2x³

a) Tìm : C(x) = A(x) - B(x)

b) Tìm Nghiệm của C(x)

Answer 1

A(x) = 5x\(^4\) - 5 + 6x\(^3\) +x\(^4\) - 5x -12

=\(6x^4+6x^3\)-5x-17

B(x) = 8x\(^4\) +2x\(^3\) - 2x\(^4\) + 4x\(^3\) - 5x - 15 - 2x\(^3\)

=\(6x^4\)+\(4x^3\)-5x-15

a,C(x)=A(x)-B(x)=(\(6x^4+6x^3\)-5x-17)-(\(6x^4\)+\(4x^3\)-5x-15)

=\(6x^4+6x^3\)-5x-17-\(6x^4\)-\(4x^3\)+5x+15

=\((6x^4-6x^4)\)+\((6x^3-4x^3)\)+(-5x+5x)+ (-17-15)

= \(2x^3-32\)

b,C(x)=0<=>\(2x^3-32=0\)

=>\(2x^3=32\)

=>\(x^3=16\)

vậy C(x) vô nghiệm