thì mik nói là mik lm sai òi mà

sai ak

mik bấm lộn

ĐK \(9a^2-b^2\ne0\)

Ta có B =\(\frac{2a-b}{3a-b}+\frac{5b-a}{3a+b}=\frac{\left(2a-b\right)\left(3a+b\right)+\left(5b-a\right)\left(3a-b\right)}{\left(3a+b\right)\left(3a-b\right)}\)

=\(\frac{6a^2+2ab-3ab-b^2+15ab-5b^2-3a^2+ab}{9a^2-b^2}\)

=\(\frac{3a^2+15ab-6b^2}{9a^2-b^2}=\frac{3\left(a^2+5ab-2b^2\right)}{9a^2-b^2}\)

Từ \(10a^2-3b^2+5ab=0\Rightarrow5ab=3b^2-10a^2\)

\(\Rightarrow B=\frac{3\left(a^2+3b^2-10a^2-2b^2\right)}{9a^2-b^2}=\frac{3\left(-9a^2+b^2\right)}{9a^2-b^2}=-3\)

Vậy B =-3

x²(y+z)+y²(z+y)+z²(x+y)

a. \(2a^2+5ab-3b^2-7b-2\)

\(=\left(2a^2+6ab+2a\right)-\left(ab+3b^2+b\right)-\left(2a+6b+2\right)\)

\(=2a\left(a+3b+1\right)-b\left(a+3b+1\right)-2\left(a+3b+1\right)\)

\(=\left(2a-b-2\right)\left(a+3b+1\right)\)

b. \(2x^2-7xy+x+3y^2-3y\)

\(=\left(2x^2-xy\right)-\left(6xy-3y^2\right)+\left(x-3y\right)\)

\(=x\left(2x-y\right)-3y\left(2x-y\right)+\left(x-3y\right)\)

\(=\left(x-3y\right)\left(2x-y\right)+\left(x-3y\right)\)

\(=\left(x-3y\right)\left(2x-y+1\right)\)

c. \(6x^2-xy-2y^2+3x-2y\)

\(=\left(6x^2+3xy\right)-\left(4xy-2y^2\right)+\left(3x-2y\right)\)

\(=3x\left(2x+y\right)-2y\left(2x+y\right)+\left(3x-2y\right)\)

\(=\left(3x-2y\right)\left(2x+y\right)+\left(3x-2y\right)\)

\(=\left(3x-2y\right)\left(2x+y+1\right)\)

\(3y^2\left(a-3x\right)-a\left(a-3x\right)=\left(3y^2-a\right)\left(a-3x\right)\)