Answer:
c) 81x² + 49x²y² - 126x²y
Explanation:
when you square something you are multiplying it by itself
(9x - 7xy)² = (9x - 7xy) (9x - 7xy)
this requires the FOIL method:
F = first = (9x)(9x) = 81x²
O = outer = (9x)(-7xy) = -63x²y
I = inner = (-7xy)(9x) = -63x²y
L = last = (-7xy)(-7xy) = 49x²y²
the two middle terms can be combined because they are 'like'
-63x²y + -63x²y = -126x²y
answer:
81x² - 126x²y + 49x²y²
the order is normally changed to be put in decreasing exponent order so 49x²y² is put before -126x²y