2x^2+6x=21

Simple and best practice solution for 2x^2+6x=21 equation. Check how easy it is, and learn it for the future. Our solution is simple, and easy to understand, so don`t hesitate to use it as a solution of your homework.

If it's not what You are looking for type in the equation solver your own equation and let us solve it.

Solution for 2x^2+6x=21 equation:


Simplifying
2x2 + 6x = 21

Reorder the terms:
6x + 2x2 = 21

Solving
6x + 2x2 = 21

Solving for variable 'x'.

Reorder the terms:
-21 + 6x + 2x2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + 6x + 2x2 = 0

Begin completing the square.  Divide all terms by
2 the coefficient of the squared term: 

Divide each side by '2'.
-10.5 + 3x + x2 = 0

Move the constant term to the right:

Add '10.5' to each side of the equation.
-10.5 + 3x + 10.5 + x2 = 0 + 10.5

Reorder the terms:
-10.5 + 10.5 + 3x + x2 = 0 + 10.5

Combine like terms: -10.5 + 10.5 = 0.0
0.0 + 3x + x2 = 0 + 10.5
3x + x2 = 0 + 10.5

Combine like terms: 0 + 10.5 = 10.5
3x + x2 = 10.5

The x term is 3x.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3x + 2.25 + x2 = 10.5 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 10.5 + 2.25

Combine like terms: 10.5 + 2.25 = 12.75
2.25 + 3x + x2 = 12.75

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 12.75

Calculate the square root of the right side: 3.570714214

Break this problem into two subproblems by setting 
(x + 1.5) equal to 3.570714214 and -3.570714214.

Subproblem 1

x + 1.5 = 3.570714214 Simplifying x + 1.5 = 3.570714214 Reorder the terms: 1.5 + x = 3.570714214 Solving 1.5 + x = 3.570714214 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = 3.570714214 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 3.570714214 + -1.5 x = 3.570714214 + -1.5 Combine like terms: 3.570714214 + -1.5 = 2.070714214 x = 2.070714214 Simplifying x = 2.070714214

Subproblem 2

x + 1.5 = -3.570714214 Simplifying x + 1.5 = -3.570714214 Reorder the terms: 1.5 + x = -3.570714214 Solving 1.5 + x = -3.570714214 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = -3.570714214 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -3.570714214 + -1.5 x = -3.570714214 + -1.5 Combine like terms: -3.570714214 + -1.5 = -5.070714214 x = -5.070714214 Simplifying x = -5.070714214

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.070714214, -5.070714214}

See similar equations:

| 8ft= | | 25-7[(4-6)-(-2-6)]= | | 14+3(x+2)=-53 | | ((30xy)/(40y^4))((24x^3)/(-21x)) | | 21+3b-11=b+4 | | 18-32m+20= | | 8x-10=80 | | z^2-(2-2i)z+12-18i=0 | | y=-5/4x-4 | | 2x^7+28x^6+90x^5= | | 6a^5(8a-5)-(8a-5)= | | 1.4x-.9=3.3 | | 9+7y=9 | | 2x+5=6x+37 | | (1/4)y-2=6-(1/4)y | | .88d+35=.83d+46 | | 1+x=7(5x+5) | | (3x/4)-1=2 | | -7x-17=4x+3(6+8x) | | -7x+4x=-6 | | 1/4(12n-8)=4n-12 | | 33x=-33 | | 4-8k=-4(3k-6) | | 5a^5(2a-7)+3(2a-7)= | | X^2+3x^2=30 | | -38+8x=6(3x+7) | | -7+5n=-7(1+6n) | | 16+3v=4v-8(v+5) | | (2/3x)-6=14 | | 4(6n+3)=12-8n | | (5x^20)+25x=0 | | -4(7+4a)-8=-13+7a |

Equations solver categories