7x^2+21x-18=0

Simple and best practice solution for 7x^2+21x-18=0 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 7x^2+21x-18=0 equation:


Simplifying
7x2 + 21x + -18 = 0

Reorder the terms:
-18 + 21x + 7x2 = 0

Solving
-18 + 21x + 7x2 = 0

Solving for variable 'x'.

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

Divide each side by '7'.
-2.571428571 + 3x + x2 = 0

Move the constant term to the right:

Add '2.571428571' to each side of the equation.
-2.571428571 + 3x + 2.571428571 + x2 = 0 + 2.571428571

Reorder the terms:
-2.571428571 + 2.571428571 + 3x + x2 = 0 + 2.571428571

Combine like terms: -2.571428571 + 2.571428571 = 0.000000000
0.000000000 + 3x + x2 = 0 + 2.571428571
3x + x2 = 0 + 2.571428571

Combine like terms: 0 + 2.571428571 = 2.571428571
3x + x2 = 2.571428571

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 = 2.571428571 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 2.571428571 + 2.25

Combine like terms: 2.571428571 + 2.25 = 4.821428571
2.25 + 3x + x2 = 4.821428571

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 4.821428571

Calculate the square root of the right side: 2.195775164

Break this problem into two subproblems by setting 
(x + 1.5) equal to 2.195775164 and -2.195775164.

Subproblem 1

x + 1.5 = 2.195775164 Simplifying x + 1.5 = 2.195775164 Reorder the terms: 1.5 + x = 2.195775164 Solving 1.5 + x = 2.195775164 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 = 2.195775164 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 2.195775164 + -1.5 x = 2.195775164 + -1.5 Combine like terms: 2.195775164 + -1.5 = 0.695775164 x = 0.695775164 Simplifying x = 0.695775164

Subproblem 2

x + 1.5 = -2.195775164 Simplifying x + 1.5 = -2.195775164 Reorder the terms: 1.5 + x = -2.195775164 Solving 1.5 + x = -2.195775164 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 = -2.195775164 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -2.195775164 + -1.5 x = -2.195775164 + -1.5 Combine like terms: -2.195775164 + -1.5 = -3.695775164 x = -3.695775164 Simplifying x = -3.695775164

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.695775164, -3.695775164}

See similar equations:

| a+a+a-20=46 | | 5x(x)-11=24 | | 8(11x-9)=0 | | 2/3p=p-9 | | 4z-2=38 | | x+x+x-x+7=x+x+x-x+12 | | -19=3y-7 | | 600-3x/2 | | 10+8(2x+4)=8-x | | 7x+1=48 | | 2n-3=n-7 | | (3)n=40+5n | | 5x-2=53 | | 3r^3+21r^2=54r | | -6x+18=7-1(4x+9) | | 5(x-3)-5=4(x-5) | | 11p-6=71 | | x+x+x+x+x=30 | | 3+3x=4x-1 | | 1.2x-.24=.7x | | 11x-12=87 | | 221+9y=613 | | x+20=82+20 | | 2(3-x)=42 | | x/2+(x-30)=180 | | 2x/8+4=-10 | | a+(a-10)+(a-15)=46 | | 2x=2(41) | | 1.25/6 | | 13x-33=7(2x-4) | | 6x+8-14x=96 | | 10x+3=113 |

Equations solver categories