(a+7)(a-3)=

Solution for (a+7)(a-3)= equation:

Simplifying
(a + 7)(a + -3) = 0

Reorder the terms:
(7 + a)(a + -3) = 0

Reorder the terms:
(7 + a)(-3 + a) = 0

Multiply (7 + a) * (-3 + a)
(7(-3 + a) + a(-3 + a)) = 0
((-3 * 7 + a * 7) + a(-3 + a)) = 0
((-21 + 7a) + a(-3 + a)) = 0
(-21 + 7a + (-3 * a + a * a)) = 0
(-21 + 7a + (-3a + a2)) = 0

Combine like terms: 7a + -3a = 4a
(-21 + 4a + a2) = 0

Solving
-21 + 4a + a2 = 0

Solving for variable 'a'.

Factor a trinomial.
(-7 + -1a)(3 + -1a) = 0

Subproblem 1
Set the factor '(-7 + -1a)' equal to zero and attempt to solve:

Simplifying
-7 + -1a = 0

Solving
-7 + -1a = 0

Move all terms containing a to the left, all other terms to the right.

Add '7' to each side of the equation.
-7 + 7 + -1a = 0 + 7

Combine like terms: -7 + 7 = 0
0 + -1a = 0 + 7
-1a = 0 + 7

Combine like terms: 0 + 7 = 7
-1a = 7

Divide each side by '-1'.
a = -7

Simplifying
a = -7
Subproblem 2
Set the factor '(3 + -1a)' equal to zero and attempt to solve:

Simplifying
3 + -1a = 0

Solving
3 + -1a = 0

Move all terms containing a to the left, all other terms to the right.

Add '-3' to each side of the equation.
3 + -3 + -1a = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -1a = 0 + -3
-1a = 0 + -3

Combine like terms: 0 + -3 = -3
-1a = -3

Divide each side by '-1'.
a = 3

Simplifying
a = 3
Solution
a = {-7, 3}