The derivative of f(x) at x=3 is 2x=6 approaching from the left side (apply power rule to y=x^2). The derivative of f(x) at x=3 is m approaching from the right side. In order for the function to be differentiable, the limit of derivative at x=3 must be the same approaching from both sides, so m=6. Then, x^2=mx+b at x=3, plug in m=6, 9=18+b, so b=-9.
Answer: 
for number 7
Step-by-step explanation:
a²+b²=c²
3²+8²=c²
9+64=c²
<u><em>(The Explanation):</em></u> What we are given is that the car drives 45 miles each hour. Furthermore, you need to multiply the amount of hours desired to the miles to get a total mile.
<u><em>(Step-By-Step Instructions):</em></u>
<em>45(4) and 45(20) </em> Multiply
<u><em>The Answers:</em></u> 4 hours = 180 miles / 20 hours = 900 miles
[ 2x + y = -9 ] x -3
[- 3x +11= y ] x 2
-6x -3y = 27
-6x + 22 = 2y
-6x +27 = 3y
-6x +22 = 2y
5 = y
-6x -3x5 = 27
-6x -15 = 27
-6x = 42
-x = 42/6
-x = 7
x = -7
answer
x = -7
y = 5
