If 21 more than 3 times a number is -15, what is the number?

The number is -12.

Step-by-step explanation:

3x+21=-15

3x=-15-21

3x=-36

x=-36/3

x=-12

-12

Step-by-step explanation:

let the number be x

"3 times a number"  : 3x

"21 more than 3 times a number" : 21 + 3x

"21 more than 3 times a number is -15" : 21 + 3x = -15

Solving this equation:

21 + 3x = -15 (subtract 21 from both sides)

3x = -15 - 21

3x = -36 (divide both sides by 3)

x = -36/3 = - 12

geometric series converge the common ratio r has magnitude less than one.

which is equivalent to

for the example we need

|2-x| < 1

-1 < 2-x   and 2-x < 1

x < 3 and x > 1

we can write that

answer: 1 < x < 3

1a. common ratio r=250/25=10 > 1     diverges

1b.   r=50/100=1/2 converges

when these converge they converge to

where a is the first term.

answer: 200

1c. r=-1   so it's not the case that |r| < 1.     diverges

2a. x is the common ratio so we converge when |x|< 1

2b.   r=-10x / -2 = 5x.

we converge when

|5x| < 1

|x| < 1/5

2c.   r=3-2x

-1 < 3-2x and 3-2x < 1

-4 < -2x and 2 < 2x

x < 2 and 1 < x

1 < x < 2

2d. [/tex] r=-48x^3/12 = 4x^3[/tex]

|4x^3| < 1

|x^3| < \frac 1 4

|x| < 4^{-1/3}

it’s the first one your welcome