List x1, x2, x3, x4 where xi is the left endpoint of the four equal intervals used to estimate the area under the curve of f(x) between x = 4 and x = 6. a 4, 4.5, 5, 5.5 b 4.5, 5, 5.5, 6 c 4.25, 4.75, 5.25, 5.75 d 4, 4.2, 5.4, 6

Option A. 4, 4.5, 5, 5.5

Step-by-step explanation:

Left point: a=x=4

Right point: b=x=6

Range: r=b-a→r=6-4→r=2

Width of each of the four equal intervals: w=2/4→w=0.5

The first left endpoint is x1=a→x1=4

The second left endpoint is x2=x1+w→x2=4+0.5→x2=4.5

The third left endpoint is x3=x2+w→x3=4.5+0.5→x3=5

The fourth left endpoint is x4=x3+w→x4=5+0.5→x4=5.5

Then, the list is: x1, x2, x3, x4 = 4, 4.5, 5, 5.5

answer;

the correct answer

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a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional