Write as a mathematical expression and solve. The sum of a number and 2 times the number is 21. Find the number. i really need help please help

3.69 (rounded)

Step-by-step explanation:

Substitute x for "a number".

New equation: x(x + 2) = 21

Distribute and combine to form a single equation: x^2 + 2x - 21 = 0

Use quadratic formula, factoring, or graphing to get all possible answers.

Quadratic formula: , where A = x^2 coefficient, B = x coefficient, and C = constant.

-5.69, 3.69

Eliminate an incorrect answer that does not line up with the above equation.

3.69

false

step-by-step explanation:

whenever we assume a point on a plane then according to geometry it will definitely have 2 dimensions and if it assumed in space then it will have 3 dimensions.

fist on the left goes with the third on the right. second on the left goes with the fourth on the right. third on the left goes with the second on the right. the fourth on the left goes with first on the right