Question

How do you evaluate b2−2c2a+c−b given a=12, b=9, c=4?

Answer 1

$9 \times 2 - 2 \times 4 \times 2 \times 12 + 4 - 9 \\ 18 - 24 \times 8 + 4 - 9 \\ 18 - 192 + 4 - 9 \\ 18 - 188 - 9 \\ 18 - 197 = - 179$