Question

xác định biểu thức A và B

a) \(\dfrac{5x}{x^2+x-6}\)=A+B

b)\(\dfrac{5x+31}{x^2-3x-10}\)=A+B

c)A+B=\(\dfrac{3x+5}{\left(x-1\right)^2}\)

d)A+B=\(\dfrac{8x+1}{x^2-8x+22}\)

Answer 1

a: \(\dfrac{5x}{x^2+x-6}=\dfrac{5x}{\left(x+3\right)\left(x-2\right)}\)

\(=\dfrac{4x+12+x-12}{\left(x+3\right)\left(x-2\right)}=\dfrac{4}{x-2}+\dfrac{x-12}{x^2+x-6}\)

=>\(A=\dfrac{4}{x-2};B=\dfrac{x-12}{x^2+x-6}\)

b: \(\dfrac{5x+31}{x^2-3x-10}=\dfrac{5x+31}{\left(x-5\right)\left(x+2\right)}\)

\(=\dfrac{3x-15+2x+46}{\left(x-5\right)\left(x+2\right)}=\dfrac{3}{x+2}+\dfrac{2x+46}{\left(x-5\right)\left(x+2\right)}\)

=>\(A=\dfrac{3}{x+2};B=\dfrac{2x+46}{\left(x-5\right)\left(x+2\right)}\)

c: \(\dfrac{3x+5}{\left(x-1\right)^2}=\dfrac{3x-3+8}{\left(x-1\right)^2}=\dfrac{3}{x-1}+\dfrac{8}{\left(x-1\right)^2}\)

=>\(A=\dfrac{3}{x-1};B=\dfrac{8}{\left(x-1\right)^2}\)