The scale factor of ∆RST to ∆DEC is 3 : 13. What is the scale factor of ∆DEC to ∆RST? Select one: a. 39 : 1 b. 1 : 39 c. 13 : 3 d. 3 : 13

ΔDEC/ΔRST is 13/3 it is c

Step-by-step explanation:

ΔRST/ΔDEC = 3/13 so the inverse is 13/3

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