2x^2+5x-21=0

Simple and best practice solution for 2x^2+5x-21=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 2x^2+5x-21=0 equation:


Simplifying
2x2 + 5x + -21 = 0

Reorder the terms:
-21 + 5x + 2x2 = 0

Solving
-21 + 5x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
-10.5 + 2.5x + x2 = 0

Move the constant term to the right:

Add '10.5' to each side of the equation.
-10.5 + 2.5x + 10.5 + x2 = 0 + 10.5

Reorder the terms:
-10.5 + 10.5 + 2.5x + x2 = 0 + 10.5

Combine like terms: -10.5 + 10.5 = 0.0
0.0 + 2.5x + x2 = 0 + 10.5
2.5x + x2 = 0 + 10.5

Combine like terms: 0 + 10.5 = 10.5
2.5x + x2 = 10.5

The x term is 2.5x.  Take half its coefficient (1.25).
Square it (1.5625) and add it to both sides.

Add '1.5625' to each side of the equation.
2.5x + 1.5625 + x2 = 10.5 + 1.5625

Reorder the terms:
1.5625 + 2.5x + x2 = 10.5 + 1.5625

Combine like terms: 10.5 + 1.5625 = 12.0625
1.5625 + 2.5x + x2 = 12.0625

Factor a perfect square on the left side:
(x + 1.25)(x + 1.25) = 12.0625

Calculate the square root of the right side: 3.473110997

Break this problem into two subproblems by setting 
(x + 1.25) equal to 3.473110997 and -3.473110997.

Subproblem 1

x + 1.25 = 3.473110997 Simplifying x + 1.25 = 3.473110997 Reorder the terms: 1.25 + x = 3.473110997 Solving 1.25 + x = 3.473110997 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.25' to each side of the equation. 1.25 + -1.25 + x = 3.473110997 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = 3.473110997 + -1.25 x = 3.473110997 + -1.25 Combine like terms: 3.473110997 + -1.25 = 2.223110997 x = 2.223110997 Simplifying x = 2.223110997

Subproblem 2

x + 1.25 = -3.473110997 Simplifying x + 1.25 = -3.473110997 Reorder the terms: 1.25 + x = -3.473110997 Solving 1.25 + x = -3.473110997 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.25' to each side of the equation. 1.25 + -1.25 + x = -3.473110997 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = -3.473110997 + -1.25 x = -3.473110997 + -1.25 Combine like terms: -3.473110997 + -1.25 = -4.723110997 x = -4.723110997 Simplifying x = -4.723110997

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.223110997, -4.723110997}

See similar equations:

| Y=4x+1.25 | | 2x^2=5x-21 | | 5x^2+1-2=0 | | (8z-u)(7z+5u)= | | 92=-5x+6(1+8x) | | 3d=2+7 | | y=20+10x | | x^2+14x+196=0 | | 4.5x=20 | | q^2-7q-60=0 | | 5c-8c=5c+48 | | 4x^2-24x+36=22 | | -8(-6x+6)=240 | | 8z(z^2+5z-3)+5z(-4z^2+z)= | | 7+5q+8-4q= | | 6i(x-4i)=8y-2i | | 5x+6=6x+11 | | 63k=9 | | -6(6-5k)-3=111 | | 0=-x^2+9x-18 | | 4tanx+5=1 | | -6x+8(-7x+5)=-332 | | -3m+28=40 | | (x-3)(x^2-4x+7)= | | 2m-(9m+6)-7m=a | | 1x-3y=-2 | | cosinex=0.6 | | 22x+199=x+10 | | 4.5y-y=-14+21 | | -(6a+6)-5(a-7)= | | 9=r-1+4 | | 7z(z^2+4z-3)+9z(-2z^2+z)= |

Equations solver categories