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
[tex]\begin{gathered} -45x+72=9(\frac{-45x}{9}+\frac{72}{9}) \\ \text{this implies that} \\ -45x+72=9(-5x+8) \end{gathered}[/tex]Therefore the correct answer 9(-5x + 8)
