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There are 3 main ways to solving a quadratic equation of the from ax2+bx+c=0
The first, also the quickest and easiest, is factorising the equation into the form of (ax+b)(bx+c)=0 implying that either x=-a/b or x=-c/b, for this equation you would factorise into (x-7)(x+3)=0
The second is to use the formula x=(-b±√(b2-4ac))/2a and just put the relative numbers in from your equation.
The final is the 'completing the square' method, where you separate the variable part into the form (x+b/2)2+c-(b/2)2=0 (here we are assuming a=1) leading to x=±√((b/2)2-c)-b/2. This may look more complicated that the formulae method but can sometimes be a lot quicker if you become used to this method and is sometimes needed when the second method leaves you with taking the squareroot of a negative number.
For the equation x2 - 4x - 21=0, it is easiest to use the first or third method, either way you obtain x=7 or -3.
What else can I help you with?
How do you solve 16t squared minus 9 equals 0?
Solve this problem -x squared -40x- 80 =0
X squared plus 6x plus 8 equals 0?
x2 + 6x + 8 = 0 Solve for x.X = -2 or X = -4
How do you solve q squared plus 16q equals 0?
By factoring. q2 + 16q = 0 q (q + 16) = 0 Now, either q = 0, or q + 16 = 0. Solve those two equations to get the solution.
How do you solve x squared minus 9 equals 0?
x * x - 9 = 0 PEMDAS = Multiplication first. What multiplied it self equals nine? 3. So x = 3
How do you solve 5x-to-the-4th minus 483x-cubed plus 94x-squared plus 126x minus 18 equals 0?
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How do you solve 16t squared minus 9 equals 0?
Solve this problem -x squared -40x- 80 =0
How do you solve x squared minus 10 equals 0?
If x squared -10 = 0 then x = the square root of 10
How do you solve 0 equals x squared minus ten x plus 16?
x^(2) - 10x + 16 = 0 Factors of '16', which are, 1,2,4,8,16. Select two numbers from this list that add/subtract to '10' . They are '2' and '8'. Setting up brackets ( x 2)(x 8) Since '16' is positive(+), then both signs must be the same. Since '10x' is negative (-) , then both signs are negative. Hence (x - 2)(x - 8 ) = 0 When x - 2 = 0 x = 2 & when x - 8 = 0 x = 8 So the two answers are ,2, & ,8, .
How do you solve 3x squared -9x equals 0?
3x2-9x = 0 x(3x-9) = 0 x = 0 or x = 3
How do you solve 3x squared plus 5x minus 25 equals 0?
x = 25 / 3squared + 5
How would you solve 'x squared equals 25x'?
X (x - 25) So X = 0 Or X = +25
X squared plus 6x plus 8 equals 0?
x2 + 6x + 8 = 0 Solve for x.X = -2 or X = -4
How do you solve q squared plus 16q equals 0?
By factoring. q2 + 16q = 0 q (q + 16) = 0 Now, either q = 0, or q + 16 = 0. Solve those two equations to get the solution.
How do you solve x squared minus 9 equals 0?
x * x - 9 = 0 PEMDAS = Multiplication first. What multiplied it self equals nine? 3. So x = 3
X squared plus y squared minus 1 all cubed then minus the product of x squared times y cubed that all equals 0 How do you solve for y?
You have to put your heart into it!
What is 0 squared?
0 squared is 0. Zero times zero equals zero.
How do you solve a squared plus a plus ab plus b equals 0?
That factors to (a + 1)(a + b) a = -1, -b b = -a
