\(-13\cdot\left(-88\right)=1144\)

\(38\cdot29=1102\)

=> -13* (-88)  > 38 *29

=> \(\frac{-13}{38}>\frac{29}{-88}\)

--------------------------------------------------------------------------------

\(\frac{-181818}{313131}=\frac{-18}{31}\) (rút gọn cho 10101)        --------------nói là rút gọn thôi chứ nhìn vào là phải bt đáp án rồi---------

=> \(\frac{-18}{31}=\frac{-181818}{313131}\)

a) \(A+B=\left(x^2-2x-y+3y-1\right)+\left(-2x^2+3y^2-5x+y+3\right)\)

                \(=-x^2+3y^2-7x+3y+2\)

\(A-B=\left(x^2-2x-y+3y-1\right)-\left(-2x^2+3y^2-5x+y+3\right)\)

           \(=3x^2-3y^2+3x+2y-4\)

b) \(A\left(1;-2\right)=1^2-2\cdot1-\left(-2\right)+3\cdot\left(-2\right)-1\)

                   \(=1-2+2-6-1\)

                   \(=-6\)

a)  \(\left(x^2-x+1\right)\cdot\left(x+1\right)-x^3+3x=15\)

\(x^3-x^2+x+x^2-x+1-x^3+3x=15\)

\(3x+1=15\)

\(x=\frac{14}{3}\)

b) \(\left(x+3\right)\left(x-2\right)+3x=4\left(x+\frac{3}{4}\right)\)

\(x^2+3x-2x-6+3x=4x+3\)

\(x^2=9\)

\(x=+-3\)

c) \(\left(x^2-5\right)\left(x+2\right)+5x=2x^2+17\)

\(x^3-5x+2x^2-10+5x=2x^2+17\)

\(x^3=27\)

\(x=3\)

Câu b):

Thêm 1 dấu = nữa:

= x⁶ - 27