First, recognize that adding and subtracting are, from one viewpoint, the same thing. Subtracting a number is the same thing as adding the negative of that number. For example, 4 – 12 is the same as 4 + –12 (which, because the order of terms doesn't matter with addition, is the same as –12 + 4). With that in mind, here are the rules for adding with negative and positive numbers:
If both numbers are positive, then the answer is positive.
If both numbers are negative, then the answer is negative.
If the numbers have different signs, the answer takes the sign of the higher number.
Subtracting a negative number is the same as adding the positive of that number. For example, 5 – –4 is the same as 5 + 4.
Multiplying and dividing with negative numbers if the numbers have different signs, the answer is negative.
Y = 9x - 5...the slope here is 9...a parallel line will have the same slope.
y = mx + b slope(m) = 9 (5,-4)...x = 5 and y = -4 now we sub and solve for b, the y int -4 = 9(5) + b -4 = 45 + b -4 - 45 = b -49 = b so ur parallel line is : y = 9x - 49
y = 9x - 5...slope is 9. A perpendicular line will have a negative reciprocal slope. All that means is " flip " the slope and change the sign. So the slope we need is -1/9.
y = mx + b slope(m) = -1/9 (5,-4)...x = 5 and y = -4 now we sub and solve for b, the y int -4 = -1/9(5) + b -4 = -5/9 + b -4 + 5/9 = b -36/9 + 5/9 = b - 31/9 = b
