Part A
(3x)^2*x^4
(3x)*(3x)*x^4 .... expand out (3x)^2
(3*3)*(x*x*x^4)
9x^6
Answer: 9x^6
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Part B
It appears that Tonya forgot to square the 3 term and had this as her steps
(3x)^2*x^4
3x^2*x^4
3x^(2*4)
3x^8
Which is incorrect as the answer in part A indicates.
Not only is the '3' part wrong, but also the exponent of 8. Instead of multiplying the exponents, she should have added them.
The rule is a^b*a^c = a^(b+c). In this case, a = x, b = 2 and c = 4.
So x^2*x^4 = x^(2+4) = x^6