Factorise X² + 4x -45
To do this, you find the factor of 45 that their sum will give 4
[tex]\begin{gathered} \text{factors of 45} \\ 45\text{ = 1}\times45,\text{ 9}\times5 \\ 9-5\text{ is 4} \end{gathered}[/tex]Then you replace the second term i.e 4x with 9x-5x
[tex]\begin{gathered} x^2+9x-5x-45 \\ \text{then take the common factor of the first two terms} \\ x(x+9)-5(x+9) \end{gathered}[/tex][tex]\begin{gathered} \text{Then take the common expr}ession \\ (x+9)(x-5)_{} \end{gathered}[/tex]Hence the complete factorization is (x+9)(x-5)