-7x^2-21x+40=0

Simple and best practice solution for -7x^2-21x+40=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+40=0 equation:


Simplifying
-7x2 + -21x + 40 = 0

Reorder the terms:
40 + -21x + -7x2 = 0

Solving
40 + -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'.
-5.714285714 + 3x + x2 = 0

Move the constant term to the right:

Add '5.714285714' to each side of the equation.
-5.714285714 + 3x + 5.714285714 + x2 = 0 + 5.714285714

Reorder the terms:
-5.714285714 + 5.714285714 + 3x + x2 = 0 + 5.714285714

Combine like terms: -5.714285714 + 5.714285714 = 0.000000000
0.000000000 + 3x + x2 = 0 + 5.714285714
3x + x2 = 0 + 5.714285714

Combine like terms: 0 + 5.714285714 = 5.714285714
3x + x2 = 5.714285714

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 = 5.714285714 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 5.714285714 + 2.25

Combine like terms: 5.714285714 + 2.25 = 7.964285714
2.25 + 3x + x2 = 7.964285714

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 7.964285714

Calculate the square root of the right side: 2.822106609

Break this problem into two subproblems by setting 
(x + 1.5) equal to 2.822106609 and -2.822106609.

Subproblem 1

x + 1.5 = 2.822106609 Simplifying x + 1.5 = 2.822106609 Reorder the terms: 1.5 + x = 2.822106609 Solving 1.5 + x = 2.822106609 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 = 2.822106609 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 2.822106609 + -1.5 x = 2.822106609 + -1.5 Combine like terms: 2.822106609 + -1.5 = 1.322106609 x = 1.322106609 Simplifying x = 1.322106609

Subproblem 2

x + 1.5 = -2.822106609 Simplifying x + 1.5 = -2.822106609 Reorder the terms: 1.5 + x = -2.822106609 Solving 1.5 + x = -2.822106609 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 = -2.822106609 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -2.822106609 + -1.5 x = -2.822106609 + -1.5 Combine like terms: -2.822106609 + -1.5 = -4.322106609 x = -4.322106609 Simplifying x = -4.322106609

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.322106609, -4.322106609}

See similar equations:

| (4x)(3x+2)= | | 15z^2+17z-18= | | m*2/3=1-13/15 | | Q=20-0.25p | | 6r^2-14r-12= | | 3x+21-21=180-21 | | 8y^2-6y-9= | | 2x^2-8x= | | 4x^3+18x^2+32= | | 3x+4(y+9)= | | 50+1.75x=39.99+2.50x | | 2(x-3)-4(x+6)=-4x-6 | | 3x+15-15=180-15 | | 2(x+5y)= | | 2(x-3)-4(x+6)=-4(x-6) | | 10x^2+48x+32= | | 5x^3-10x^2-15x= | | x+x+(x+15)= | | 39.99+2.50x=100 | | 81x^2-49y^2= | | 4x+(90-x)=180 | | (34-x)+6=35 | | 6x^8-10x^4y= | | 12x^2+11x-5= | | 12x^2+11x+-4= | | (23-x)+4=26 | | 8z=56 | | -6x^2-13x-5=0 | | 5(w+2)=6(w-2) | | 2ab^2-10a^3+6a= | | (4x-8)+34+(76-x)=180 | | 11x^2-23= |

Equations solver categories