Answer:
x=4
Step-by-step explanation:
well you know that the square is 90 degrees so you set it up as 90=21x+6. Then you subtract 6 from both sides and it gets you 84=21x. Then divide 21 on both sides. So the answer is x=4
B.
That would be y = (x +10)^2.
-19
-4 * -4 - 12 + 9
-16-12 +9
-28 + 9
