Find the missing length with mark with a question mark. part 2

  104

Step-by-step explanation:

You have to be careful with this one, as the picture is misleading.

  RS/RT = RE/RD . . . . . . . corresponding sides are proportional

  RS/169 = 24/39 . . . . . . . fill in the given values

  RS = 169·24/39 = 104

104

Step-by-step explanation:

It tells us the triangles are similar because of the ~.

The order matters in this statement: RST~RED.

It tells us which sides are proportional:

So we are given DR=39 and ER=24 and RT=169.

Let's see which part of our equation we wrote that we can use.

Note: RT is same as TR. ER is same as RE.  

We are using first and the last fraction of what I wrote:

To solve for ? just multiply both sides by 24:

step-by-step explanation: yes

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15