Correct so expression= 4ab(25a^4-9b^2)= 4ab(5a^2-3b)(5a^2+3b)
You have the 2nd question correct
First question:
How do you factor when you have multiple variables?
Factor completely:
100a^{5}b - 36ab^{3}
4 will factor into both 100 and 36. And ab will factor into both the variable parts?
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Second:
Factor completely:
m^{3}- 64
m^{3} - 64 = (m-4)(m^{2}+4m+16)
Is that correct?