SOLUTION: what is the value of x using the equation {{{x^2+4x-21=0}}}

Question 254065: what is the value of x using the equation
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
x^2+4x-21=0 is a quadratic equation.
It can be factored into
(x-3)(x+7)=0
so that its solutions (roots ) are 3 and -7

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=100 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 3, -7. Here's your graph:

RELATED QUESTIONS
Solve by factoring and using the principle of zero products:... (answered by Alan3354)

Solve by factoring and using the principle of zero products: x^2 + 4x - 21 = 0 (answered by jsmallt9)

Solve by factoring and using the principle of zero products: x^2+4x-21=0 (answered by lynnlo)

What is the value of x in the equation 4x-2(x+3)=8 (answered by greenestamps)

What is the answer to the following equation. x^2-4x+c=0 Find the value of... (answered by Alan3354)

what is the value of x in the equation {6x+5y=245 ; 4x+3y=155 using elimination by... (answered by mananth)

Please show me how to solve the equation using the Zero-factor property. Thanks!... (answered by tutorcecilia)

If (x+5)-2(4x-1)=0, what is the value of... (answered by josmiceli,josgarithmetic)

If x<0 and 4x^2=-9x+55, what is the value of... (answered by Alan3354)