Find the 15th term of the arithmetic sequence 2x+7, 6x+11, 10x+15,

a15 = 58x + 63

Step-by-step explanation:

number of terms (n) = 15

first term (a1) = 2x + 7

second term (a2) = 6x + 11

common difference (d) = a2-a1 = 6x + 11 - (2x + 7)

                                                   = 6x + 11 - 2x - 7

                                                   = 4x + 4

                                                   = 4(x + 1)

15th term (a15) = ?

                                  equation :

                  a15 = a1 + (n - 1) × d

                  a15 = 2x + 7 + (15 - 1) × 4(x + 1)

                  a15 = 2x + 7 + 14 × 4 × (x + 1)

                  a15 = 2x + 7 +  56(x + 1)

                  a15 = 2x + 7 +  56x + 56

                  a15 = 58x + 63

set each factor equal to 0

4x-3 = 0

2x-1 = 0

solve for x.

4x-3=0

4x=3

x= 3/4

solve for x. 

2x-1= 0

2x= 1

x= 1/2

eventually after a few more steps, your answer should be 1/2 is less than or equal to x and 3/4 is greater than or equal to x

the surface area is 124cm²

step-by-step explanation:

length: 4cm

width: 9cm

height:   2cm