I only have the time to solve for the factoring bit, but I'll explain the other 2
Factoring
Start by finding the factors of (+) 35 that add up to -12.
If you are familiar with the multiplication table and its contents, 7 and 5 come to mind relatively quickly.
You can negate both factors, knowing that negative numbers produce positive products.
We can confirm that -7 and -5 fulfill the two conditions first stated, but I'll leave that to you if you wish to do so.
We can write two binomials, of the form x + a, where a is an identified factor [(x - 7) and (x - 5)].
Write both of these binomials multiplied, and equate their product to 0.
(x - 7) (x - 5) = 0
You can then work with this to find the roots of the equation, knowing that any number times 0 is equal to 0.
2.) Quad. formula
x = −b ± √(b2 − 4ac)/2a
All you have to do is substitute values, and simplify the equation.
3.) Completing the square
I think it'd be best for you to look at visual interpretations of completing the square to get to know it intuitively. But, simply transpose the constant term c to the right side of the equation, and then replace it with the square of half of b, adding it to both equations.
Answers & Comments
I suppose you mean to solve the equation by:
I only have the time to solve for the factoring bit, but I'll explain the other 2
Factoring
Start by finding the factors of (+) 35 that add up to -12.
If you are familiar with the multiplication table and its contents, 7 and 5 come to mind relatively quickly.
You can negate both factors, knowing that negative numbers produce positive products.
We can confirm that -7 and -5 fulfill the two conditions first stated, but I'll leave that to you if you wish to do so.
We can write two binomials, of the form x + a, where a is an identified factor [(x - 7) and (x - 5)].
Write both of these binomials multiplied, and equate their product to 0.
(x - 7) (x - 5) = 0
You can then work with this to find the roots of the equation, knowing that any number times 0 is equal to 0.
2.) Quad. formula
x = −b ± √(b2 − 4ac)/2a
All you have to do is substitute values, and simplify the equation.
3.) Completing the square
I think it'd be best for you to look at visual interpretations of completing the square to get to know it intuitively. But, simply transpose the constant term c to the right side of the equation, and then replace it with the square of half of b, adding it to both equations.
Hope this helps! :)