Step 1:
Find the greatest common factor of -45x and +72.
3 | -45x | +72
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3 | -15x | +24
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| -5x | +8
Therefore, the greatest common factor of -45x and +72 is 3 x 3 = 9
Step 2:
Factor out the greatest common factor
![\begin{gathered} -45x+72=9((-45x)/(9)+(72)/(9)) \\ \text{this implies that} \\ -45x+72=9(-5x+8) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/cwc7e3yjnaqw09xmewugd5qsymie4rbwzu.png)
Therefore the correct answer 9(-5x + 8)