Write each of the following expressions without using absolute value. |a−7|−|a−9|, if a<7
PLEASE HELP D:

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If a < 7, then |a-7| = -(a-7) = -a+7 based on how absolute value functions are constructed. We're using the idea that

Also, if a < 7, then |a-9| = -(a-9) = -a+9. This is true whenever 'a' is less than 9 for similar reasoning as above.

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So we have,

|a-7| - |a-9| = -a+7 - (-a+9) = -a+7+a-9 = -2

As long as a < 7, the result of |a-7| - |a-9| will always be -2.

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As an example, let's say a = 0

|a-7| - |a-9| = |0-7| - |0-9|

|a-7| - |a-9| = |-7| - |-9|

|a-7| - |a-9| = 7 - 9

|a-7| - |a-9| = -2

I recommend you try out other values of 'a' to see if you get -2 or not. Of course only pick values that are smaller than 7.

step-by-step explanation:

(b) 240

step-by-step explanation:

first, we use the pythagorean formula using the given side lengths to find x. then we use x to find the side lengths. then we add the side lengths to find the perimeter.

pythagorean theorem formula:

a^2 + b^2 = c^2

(x - 20)^2 + (x - 40)^2 = x^2

x^2 - 40x + 400 + x^2 - 80x + 1600 = x^2

x^2 -120x + 2000 = 0

(x - 100)(x - 20) = 0

x - 100 = 0 or x - 20 = 0

x = 100 or x = 20

we see that the solution x = 20 must be discarded because it will give a negative side length and a side length of 0. the only valid solution is x = 100.

perimeter = sum of the lengths of the sides

perimeter = x + x - 20 + x - 40

perimeter = 3x - 60

replace x with 100.

perimeter = 3(100) - 60

perimeter = 300 - 60

perimeter = 240