Solve for a
a=-6
Share
Copied to clipboard
5-3a-\left(a+1\right)\left(2a+2\right)=\left(a+3\right)\left(3-a\right)
Variable a cannot be equal to any of the values -3,-1 since division by zero is not defined. Multiply both sides of the equation by \left(a+1\right)\left(a+3\right), the least common multiple of a^{2}+4a+3,a+3,a+1.
5-3a-\left(2a^{2}+4a+2\right)=\left(a+3\right)\left(3-a\right)
Use the distributive property to multiply a+1 by 2a+2 and combine like terms.
5-3a-2a^{2}-4a-2=\left(a+3\right)\left(3-a\right)
To find the opposite of 2a^{2}+4a+2, find the opposite of each term.
5-7a-2a^{2}-2=\left(a+3\right)\left(3-a\right)
Combine -3a and -4a to get -7a.
3-7a-2a^{2}=\left(a+3\right)\left(3-a\right)
Subtract 2 from 5 to get 3.
3-7a-2a^{2}=9-a^{2}
Consider \left(a+3\right)\left(3-a\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}. Square 3.
3-7a-2a^{2}-9=-a^{2}
Subtract 9 from both sides.
-6-7a-2a^{2}=-a^{2}
Subtract 9 from 3 to get -6.
-6-7a-2a^{2}+a^{2}=0
Add a^{2} to both sides.
-6-7a-a^{2}=0
Combine -2a^{2} and a^{2} to get -a^{2}.
-a^{2}-7a-6=0
Rearrange the polynomial to put it in standard form. Place the terms in order from highest to lowest power.
a+b=-7 ab=-\left(-6\right)=6
To solve the equation, factor the left hand side by grouping. First, left hand side needs to be rewritten as -a^{2}+aa+ba-6. To find a and b, set up a system to be solved.
-1,-6 -2,-3
Since ab is positive, a and b have the same sign. Since a+b is negative, a and b are both negative. List all such integer pairs that give product 6.
-1-6=-7 -2-3=-5
Calculate the sum for each pair.
a=-1 b=-6
The solution is the pair that gives sum -7.
\left(-a^{2}-a\right)+\left(-6a-6\right)
Rewrite -a^{2}-7a-6 as \left(-a^{2}-a\right)+\left(-6a-6\right).
a\left(-a-1\right)+6\left(-a-1\right)
Factor out a in the first and 6 in the second group.
\left(-a-1\right)\left(a+6\right)
Factor out common term -a-1 by using distributive property.
a=-1 a=-6
To find equation solutions, solve -a-1=0 and a+6=0.
a=-6
Variable a cannot be equal to -1.
5-3a-\left(a+1\right)\left(2a+2\right)=\left(a+3\right)\left(3-a\right)
Variable a cannot be equal to any of the values -3,-1 since division by zero is not defined. Multiply both sides of the equation by \left(a+1\right)\left(a+3\right), the least common multiple of a^{2}+4a+3,a+3,a+1.
5-3a-\left(2a^{2}+4a+2\right)=\left(a+3\right)\left(3-a\right)
Use the distributive property to multiply a+1 by 2a+2 and combine like terms.
5-3a-2a^{2}-4a-2=\left(a+3\right)\left(3-a\right)
To find the opposite of 2a^{2}+4a+2, find the opposite of each term.
5-7a-2a^{2}-2=\left(a+3\right)\left(3-a\right)
Combine -3a and -4a to get -7a.
3-7a-2a^{2}=\left(a+3\right)\left(3-a\right)
Subtract 2 from 5 to get 3.
3-7a-2a^{2}=9-a^{2}
Consider \left(a+3\right)\left(3-a\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}. Square 3.
3-7a-2a^{2}-9=-a^{2}
Subtract 9 from both sides.
-6-7a-2a^{2}=-a^{2}
Subtract 9 from 3 to get -6.
-6-7a-2a^{2}+a^{2}=0
Add a^{2} to both sides.
-6-7a-a^{2}=0
Combine -2a^{2} and a^{2} to get -a^{2}.
-a^{2}-7a-6=0
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.
a=\frac{-\left(-7\right)±\sqrt{\left(-7\right)^{2}-4\left(-1\right)\left(-6\right)}}{2\left(-1\right)}
This equation is in standard form: ax^{2}+bx+c=0. Substitute -1 for a, -7 for b, and -6 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
a=\frac{-\left(-7\right)±\sqrt{49-4\left(-1\right)\left(-6\right)}}{2\left(-1\right)}
Square -7.
a=\frac{-\left(-7\right)±\sqrt{49+4\left(-6\right)}}{2\left(-1\right)}
Multiply -4 times -1.
a=\frac{-\left(-7\right)±\sqrt{49-24}}{2\left(-1\right)}
Multiply 4 times -6.
a=\frac{-\left(-7\right)±\sqrt{25}}{2\left(-1\right)}
Add 49 to -24.
a=\frac{-\left(-7\right)±5}{2\left(-1\right)}
Take the square root of 25.
a=\frac{7±5}{2\left(-1\right)}
The opposite of -7 is 7.
a=\frac{7±5}{-2}
Multiply 2 times -1.
a=\frac{12}{-2}
Now solve the equation a=\frac{7±5}{-2} when ± is plus. Add 7 to 5.
a=-6
Divide 12 by -2.
a=\frac{2}{-2}
Now solve the equation a=\frac{7±5}{-2} when ± is minus. Subtract 5 from 7.
a=-1
Divide 2 by -2.
a=-6 a=-1
The equation is now solved.
a=-6
Variable a cannot be equal to -1.
5-3a-\left(a+1\right)\left(2a+2\right)=\left(a+3\right)\left(3-a\right)
Variable a cannot be equal to any of the values -3,-1 since division by zero is not defined. Multiply both sides of the equation by \left(a+1\right)\left(a+3\right), the least common multiple of a^{2}+4a+3,a+3,a+1.
5-3a-\left(2a^{2}+4a+2\right)=\left(a+3\right)\left(3-a\right)
Use the distributive property to multiply a+1 by 2a+2 and combine like terms.
5-3a-2a^{2}-4a-2=\left(a+3\right)\left(3-a\right)
To find the opposite of 2a^{2}+4a+2, find the opposite of each term.
5-7a-2a^{2}-2=\left(a+3\right)\left(3-a\right)
Combine -3a and -4a to get -7a.
3-7a-2a^{2}=\left(a+3\right)\left(3-a\right)
Subtract 2 from 5 to get 3.
3-7a-2a^{2}=9-a^{2}
Consider \left(a+3\right)\left(3-a\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}. Square 3.
3-7a-2a^{2}+a^{2}=9
Add a^{2} to both sides.
3-7a-a^{2}=9
Combine -2a^{2} and a^{2} to get -a^{2}.
-7a-a^{2}=9-3
Subtract 3 from both sides.
-7a-a^{2}=6
Subtract 3 from 9 to get 6.
-a^{2}-7a=6
Quadratic equations such as this one can be solved by completing the square. In order to complete the square, the equation must first be in the form x^{2}+bx=c.
\frac{-a^{2}-7a}{-1}=\frac{6}{-1}
Divide both sides by -1.
a^{2}+\left(-\frac{7}{-1}\right)a=\frac{6}{-1}
Dividing by -1 undoes the multiplication by -1.
a^{2}+7a=\frac{6}{-1}
Divide -7 by -1.
a^{2}+7a=-6
Divide 6 by -1.
a^{2}+7a+\left(\frac{7}{2}\right)^{2}=-6+\left(\frac{7}{2}\right)^{2}
Divide 7, the coefficient of the x term, by 2 to get \frac{7}{2}. Then add the square of \frac{7}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
a^{2}+7a+\frac{49}{4}=-6+\frac{49}{4}
Square \frac{7}{2} by squaring both the numerator and the denominator of the fraction.
a^{2}+7a+\frac{49}{4}=\frac{25}{4}
Add -6 to \frac{49}{4}.
\left(a+\frac{7}{2}\right)^{2}=\frac{25}{4}
Factor a^{2}+7a+\frac{49}{4}. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.
\sqrt{\left(a+\frac{7}{2}\right)^{2}}=\sqrt{\frac{25}{4}}
Take the square root of both sides of the equation.
a+\frac{7}{2}=\frac{5}{2} a+\frac{7}{2}=-\frac{5}{2}
Simplify.
a=-1 a=-6
Subtract \frac{7}{2} from both sides of the equation.
a=-6
Variable a cannot be equal to -1.
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}