Factor
\left(d-29\right)\left(d+1\right)
Evaluate
\left(d-29\right)\left(d+1\right)
Share
Copied to clipboard
a+b=-28 ab=1\left(-29\right)=-29
Factor the expression by grouping. First, the expression needs to be rewritten as d^{2}+ad+bd-29. To find a and b, set up a system to be solved.
a=-29 b=1
Since ab is negative, a and b have the opposite signs. Since a+b is negative, the negative number has greater absolute value than the positive. The only such pair is the system solution.
\left(d^{2}-29d\right)+\left(d-29\right)
Rewrite d^{2}-28d-29 as \left(d^{2}-29d\right)+\left(d-29\right).
d\left(d-29\right)+d-29
Factor out d in d^{2}-29d.
\left(d-29\right)\left(d+1\right)
Factor out common term d-29 by using distributive property.
d^{2}-28d-29=0
Quadratic polynomial can be factored using the transformation ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right), where x_{1} and x_{2} are the solutions of the quadratic equation ax^{2}+bx+c=0.
d=\frac{-\left(-28\right)±\sqrt{\left(-28\right)^{2}-4\left(-29\right)}}{2}
All equations of the form ax^{2}+bx+c=0 can be solved using the quadratic formula: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. The quadratic formula gives two solutions, one when ± is addition and one when it is subtraction.
d=\frac{-\left(-28\right)±\sqrt{784-4\left(-29\right)}}{2}
Square -28.
d=\frac{-\left(-28\right)±\sqrt{784+116}}{2}
Multiply -4 times -29.
d=\frac{-\left(-28\right)±\sqrt{900}}{2}
Add 784 to 116.
d=\frac{-\left(-28\right)±30}{2}
Take the square root of 900.
d=\frac{28±30}{2}
The opposite of -28 is 28.
d=\frac{58}{2}
Now solve the equation d=\frac{28±30}{2} when ± is plus. Add 28 to 30.
d=29
Divide 58 by 2.
d=-\frac{2}{2}
Now solve the equation d=\frac{28±30}{2} when ± is minus. Subtract 30 from 28.
d=-1
Divide -2 by 2.
d^{2}-28d-29=\left(d-29\right)\left(d-\left(-1\right)\right)
Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute 29 for x_{1} and -1 for x_{2}.
d^{2}-28d-29=\left(d-29\right)\left(d+1\right)
Simplify all the expressions of the form p-\left(-q\right) to p+q.
x ^ 2 -28x -29 = 0
Quadratic equations such as this one can be solved by a new direct factoring method that does not require guess work. To use the direct factoring method, the equation must be in the form x^2+Bx+C=0.
r + s = 28 rs = -29
Let r and s be the factors for the quadratic equation such that x^2+Bx+C=(x−r)(x−s) where sum of factors (r+s)=−B and the product of factors rs = C
r = 14 - u s = 14 + u
Two numbers r and s sum up to 28 exactly when the average of the two numbers is \frac{1}{2}*28 = 14. You can also see that the midpoint of r and s corresponds to the axis of symmetry of the parabola represented by the quadratic equation y=x^2+Bx+C. The values of r and s are equidistant from the center by an unknown quantity u. Express r and s with respect to variable u. <div style='padding: 8px'><img src='https://opalmath.azureedge.net/customsolver/quadraticgraph.png' style='width: 100%;max-width: 700px' /></div>
(14 - u) (14 + u) = -29
To solve for unknown quantity u, substitute these in the product equation rs = -29
196 - u^2 = -29
Simplify by expanding (a -b) (a + b) = a^2 – b^2
-u^2 = -29-196 = -225
Simplify the expression by subtracting 196 on both sides
u^2 = 225 u = \pm\sqrt{225} = \pm 15
Simplify the expression by multiplying -1 on both sides and take the square root to obtain the value of unknown variable u
r =14 - 15 = -1 s = 14 + 15 = 29
The factors r and s are the solutions to the quadratic equation. Substitute the value of u to compute the r and s.
Examples
Quadratic equation
{ x } ^ { 2 } - 4 x - 5 = 0
Trigonometry
4 \sin \theta \cos \theta = 2 \sin \theta
Linear equation
y = 3x + 4
Arithmetic
699 * 533
Matrix
\left[ \begin{array} { l l } { 2 } & { 3 } \\ { 5 } & { 4 } \end{array} \right] \left[ \begin{array} { l l l } { 2 } & { 0 } & { 3 } \\ { -1 } & { 1 } & { 5 } \end{array} \right]
Simultaneous equation
\left. \begin{cases} { 8x+2y = 46 } \\ { 7x+3y = 47 } \end{cases} \right.
Differentiation
\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
Integration
\int _ { 0 } ^ { 1 } x e ^ { - x ^ { 2 } } d x
Limits
\lim _{x \rightarrow-3} \frac{x^{2}-9}{x^{2}+2 x-3}