Answer:
[tex]b=-5, -7[/tex]
Step-by-step explanation:
We have the equation [tex]b^2+35=-12b[/tex] and we want to solve it by factoring.
First, let's move all the stuff to one side so that the other side is 0. So, let's add [tex]12b[/tex] to both sides. This yields:
[tex]b^2+12b+35=0[/tex]
Let's review how to factor. If we have an equation in the following form:
[tex]ax^2+bx+c=0[/tex]
Where a, b, and c are the coefficients of the variable (in our example, our variable is b), then we must find two numbers, p and q, such that:
[tex]pq=ac \text{ (p times q equals a times c) and}\\p+q=b \text{ (p plus q equals b)}[/tex]
Our equation can be rewritten as:
[tex](1)b^2+(12)b+(35)=0[/tex]
So, our a is 1, b is 12, and c is 35.
Therefore, we need to find two numbers that when multiplied together yields a(c) = 1(35) = 35 and we added together yields b = 12.
From here, we just have to guess and check. We can start by listing all the factors of 35. There aren't in fact that many:
[tex]35: 1\text{ and } 35, 5\text{ and } 7[/tex]
1 + 35 is 36, not 12. However, 5 + 7 is indeed 12. So, our two numbers p and q are 5 and 7.
Now what we've found our two numbers, we substitute the b term for our two numbers. We have:
[tex]b^2+12b+35=0[/tex]
We will substitute 12b for 5b + 7b:
[tex]b^2+5b+7b+35=0[/tex]
From here, we factor by grouping. From the first two terms, factor out a b:
[tex]b(b+5)+7b+35=0[/tex]
And from the last two terms, factor out a 7:
[tex]b(b+5)+7(b+5)=0[/tex]
Now, notice that both terms have a [tex](b+5)[/tex]. So, by using grouping or the reverse of the distribute property, we can write:
[tex](b+7)(b+5)=0[/tex]
Notice that if we distribute the left term into the right, we get [tex]b(b+5)+7(b+5)=0[/tex], so our equation is indeed equivalent.
So now we. have:
[tex](b+7)(b+5)=0[/tex]
We can now use the Zero Product Property to acquire:
[tex]b+7=0\text{ or } b+5=0[/tex]
Solve for b for each case. Therefore, the solutions of our equation are:
[tex]b=-7\text{ or } b=-5[/tex]
Notes:
If we can't find two numbers p and q that satisfy our conditions, this means that the equation cannot be factored. So, we will use alternative methods to solve our equation.
