# Giúp mk vs ạ cảm ơn bạn nhiều lắm

Giúp mk vs ạ cảm ơn bạn nhiều lắm

### 0 thoughts on “Giúp mk vs ạ cảm ơn bạn nhiều lắm”

1. minhkhang

Đáp án:

$\begin{array}{l} a){x^2} + 5x – 6\\ = {x^2} + 6x – x – 6\\ = \left( {x + 6} \right)\left( {x – 1} \right)\\ b){x^2} – 7x + 10\\ = {x^2} – 2x – 5x + 10\\ = \left( {x – 2} \right)\left( {x – 5} \right)\\ c){x^3} + {x^2} – 3x – 27\\ = {x^3} – 27 + {x^2} – 3x\\ = \left( {x – 3} \right)\left( {{x^2} + 3x + 9} \right) + x\left( {x – 3} \right)\\ = \left( {x – 3} \right)\left( {{x^2} + 3x + 9 + x} \right)\\ = \left( {x – 3} \right)\left( {{x^2} + 4x + 9} \right)\\ d)2{x^3} + 3{x^2} – 2x\\ = x.\left( {2{x^2} + 3x – 2} \right)\\ = x\left( {2{x^2} + 4x – x – 2} \right)\\ = x\left( {x + 2} \right)\left( {2x – 1} \right)\\ e){x^2} – xz – 9{y^2} + 3yz\\ = {x^2} – 9{y^2} + 3yz – xz\\ = \left( {x – 3y} \right)\left( {x + 3y} \right) – z\left( {x – 3y} \right)\\ = \left( {x – 3y} \right)\left( {x + 3y – z} \right)\\ f)\left( {x + 1} \right)\left( {x + 2} \right)\left( {x + 3} \right)\left( {x + 4} \right) – 120\\ = \left( {x + 1} \right)\left( {x + 4} \right)\left( {x + 2} \right)\left( {x + 3} \right) – 120\\ = \left( {{x^2} + 5x + 4} \right)\left( {{x^2} + 5x + 6} \right) – 120\\ Dat:{x^2} + 5x + 4 = a\\ \Rightarrow a.\left( {a + 2} \right) – 120\\ = {a^2} + 2a – 120\\ = {a^2} + 12a – 10a – 120\\ = \left( {a + 12} \right)\left( {a – 10} \right)\\ = \left( {{x^2} + 5x + 4 + 12} \right)\left( {{x^2} + 5x + 4 – 10} \right)\\ = \left( {{x^2} + 5x + 16} \right)\left( {{x^2} + 5x – 6} \right)\\ g){x^3} – 5{x^2} – 4x + 20\\ = {x^2}\left( {x – 5} \right) – 4\left( {x – 5} \right)\\ = \left( {x – 5} \right)\left( {{x^2} – 4} \right)\\ = \left( {x – 5} \right)\left( {x – 2} \right)\left( {x + 2} \right) \end{array}$