Question

[Đào Đức Hiếu]

Answer 1

[Kiều Vũ Linh]

Sắp xếp:

A(x) = -2x² + 3x - 4x³ + 3/5 - 5x⁴

= -5x⁴ - 4x³ - 2x² + 3x + 3/5

B(x) = 3x⁴ + 1/5 - 7x² + 5x³ - 9x

= 3x⁴ + 5x³ - 7x² - 9x + 1/5

--------

A(x) + B(x) = (-5x⁴ - 4x³ - 2x² + 3x + 3/5) + (3x⁴ + 5x³ - 7x² - 9x + 1/5)

= -5x⁴ - 4x³ - 2x² + 3x + 3/5 + 3x⁴ + 5x³ - 7x² - 9x + 1/5

= (-5x⁴ + 3x⁴) + (-4x³ + 5x³) + (-2x² - 7x²) + (3x - 9x) + (3/5 + 1/5)

= -2x⁴ + x³ - 9x² - 6x + 4/5

-----------

A(x) - B(x) = (-5x⁴ - 4x³ - 2x² + 3x + 3/5) - (3x⁴ + 5x³ - 7x² - 9x + 1/5)

= -5x⁴ - 4x³ - 2x² + 3x + 3/5 - 3x⁴ - 5x³ + 7x² + 9x - 1/5

= (-5x⁴ - 3x⁴) + (-4x³ - 5x³) + (-2x² + 7x²) + (3x + 9x) + (3/5 - 1/5)

= -8x⁴ - 9x³ + 5x² + 12x + 2/5

Answer 2

[HT.Phong (9A5)]

Sắp xếp:

\(A=-2x^2+3x-4x^3+\dfrac{3}{5}-5x^4=-5x^4-4x^3-2x^2+3x+\dfrac{3}{5}\)

\(B=3x^4+\dfrac{1}{5}-7x^2+5x^3-9x=3x^4+5x^3-7x^2-9x+\dfrac{1}{5}\) 

Tính: 

\(A\left(x\right)+B\left(x\right)\)

\(=-5x^4-4x^3-2x^2+3x+\dfrac{3}{5}+3x^4+5x^3-7x^2-9x+\dfrac{1}{5}\)

\(=\left(-5x^4+3x^4\right)+\left(-4x^3+5x^3\right)+\left(-2x^2-7x^2\right)+\left(3x-9x\right)+\left(\dfrac{3}{5}+\dfrac{1}{5}\right)\)

\(=-2x^4+x^3-9x^2-6x+\dfrac{4}{5}\)

\(A\left(x\right)-B\left(x\right)\)

\(=\left(-5x^4-4x^3-2x^2+3x+\dfrac{3}{5}\right)-\left(3x^4+5x^3-7x^2-9x+\dfrac{1}{5}\right)\)

\(=-5x^4-4x^3-2x^2+3x+\dfrac{3}{5}-3x^4-5x^3+7x^2+9x-\dfrac{1}{5}\)

\(=\left(-5x^4-3x^4\right)+\left(-4x^3-5x^3\right)+\left(-2x^2+7x^2\right)+\left(3x+9x\right)+\left(\dfrac{3}{5}-\dfrac{1}{5}\right)\)

\(=-8x^4-8x^3+5x^2+12x+\dfrac{2}{5}\)