4x^2-15x-21=0

Simple and best practice solution for 4x^2-15x-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 4x^2-15x-21=0 equation:


Simplifying
4x2 + -15x + -21 = 0

Reorder the terms:
-21 + -15x + 4x2 = 0

Solving
-21 + -15x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
-5.25 + -3.75x + x2 = 0

Move the constant term to the right:

Add '5.25' to each side of the equation.
-5.25 + -3.75x + 5.25 + x2 = 0 + 5.25

Reorder the terms:
-5.25 + 5.25 + -3.75x + x2 = 0 + 5.25

Combine like terms: -5.25 + 5.25 = 0.00
0.00 + -3.75x + x2 = 0 + 5.25
-3.75x + x2 = 0 + 5.25

Combine like terms: 0 + 5.25 = 5.25
-3.75x + x2 = 5.25

The x term is -3.75x.  Take half its coefficient (-1.875).
Square it (3.515625) and add it to both sides.

Add '3.515625' to each side of the equation.
-3.75x + 3.515625 + x2 = 5.25 + 3.515625

Reorder the terms:
3.515625 + -3.75x + x2 = 5.25 + 3.515625

Combine like terms: 5.25 + 3.515625 = 8.765625
3.515625 + -3.75x + x2 = 8.765625

Factor a perfect square on the left side:
(x + -1.875)(x + -1.875) = 8.765625

Calculate the square root of the right side: 2.960679821

Break this problem into two subproblems by setting 
(x + -1.875) equal to 2.960679821 and -2.960679821.

Subproblem 1

x + -1.875 = 2.960679821 Simplifying x + -1.875 = 2.960679821 Reorder the terms: -1.875 + x = 2.960679821 Solving -1.875 + x = 2.960679821 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.875' to each side of the equation. -1.875 + 1.875 + x = 2.960679821 + 1.875 Combine like terms: -1.875 + 1.875 = 0.000 0.000 + x = 2.960679821 + 1.875 x = 2.960679821 + 1.875 Combine like terms: 2.960679821 + 1.875 = 4.835679821 x = 4.835679821 Simplifying x = 4.835679821

Subproblem 2

x + -1.875 = -2.960679821 Simplifying x + -1.875 = -2.960679821 Reorder the terms: -1.875 + x = -2.960679821 Solving -1.875 + x = -2.960679821 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.875' to each side of the equation. -1.875 + 1.875 + x = -2.960679821 + 1.875 Combine like terms: -1.875 + 1.875 = 0.000 0.000 + x = -2.960679821 + 1.875 x = -2.960679821 + 1.875 Combine like terms: -2.960679821 + 1.875 = -1.085679821 x = -1.085679821 Simplifying x = -1.085679821

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.835679821, -1.085679821}

See similar equations:

| 13-v=105 | | 16x^2+60x+100=0 | | 4x+5x-10+3x+25=180 | | 25x^2+40x=20 | | 44=.5h(11) | | t+9+18=102 | | 59=h+6 | | 0.4x^6-2x^2+1.6=0 | | 47=16+p-10+11-15 | | 0.5(x+15)+0.4(x+25)=31 | | 51=3-17+e-7 | | 19-5-3+1+j=100 | | 2x+12=3x+24-x | | -(7y+1)-(-6y-3)=-5 | | 3x-6=x^2-x-6 | | -(7y+1)-(-6y-3)=5 | | 5-26=c | | n^2+6n-65=0 | | 8b+6b+2b-3= | | 180-256x+48x^2=100 | | 50+h=9 | | 3+15a^4= | | 3(5x-4)=0 | | 22=-8+3(x+4) | | 3(4c-2)=12x | | 2(x+18)=24 | | 7x-3-4x=2 | | 2(a^2+8+12)=0 | | 6.21y+3-4.5y+1.45=3.5y+6.2-2.8y+y | | X-0.20x=88.08 | | 10-n=18 | | 2(a^2+20)=0 |

Equations solver categories