Final answer:
To factor the expression -7x^3+21x^2+3x-9 by grouping, we can factor out the common binomial factor of (x-3) from each group.
Step-by-step explanation:
To factor the expression -7x3+21x2+3x-9 by grouping, we can group the terms in pairs:
Group 1: -7x3+21x2
Group 2: 3x-9
Now we can factor out the common factor in each group:
Group 1: -7x2(x-3)
Group 2: 3(x-3)
Finally, we can factor out the common binomial factor of (x-3) from both groups:
-7x3+21x2+3x-9 = (x-3)(-7x2+3)