Would someone be able to explain to me how to solve these problems? i don't need the solutions, i just need an explanation. i need to solve the quadratic by factoring.

The first 3  are examples of the difference of 2 squares so you use the identity 
a^2 - b^2 = (a + b)(a - b)
x^2 - 49 = 0 
so (x + 7)(x - 7) = 0
so either x + 7 = 0 or x - 7 = 0
giving x = -7  and 7.
Number 7 reduces to 3x^2 =12, x^2  = 4 so x = +/- 2
Number 8  take out GCf (d) to give 
d(d - 2)  = 0   so d = 0 ,  2
9 and 10 are more difficult to factor
you use the 'ac' method  Google it to get more details
2x^2 - 5x + 2
multiply first coefficient by the constant at the end 
that is 2 * 2 =  4
Now we want  2 numbers  which when multiplied give + 4 and when added give - 5:-    -1 and -4  seem promising so we write the equation as:-

2x^2 - 4x - x + 2 = 0

now factor by grouping 
2x(x - 2) - 1(x - 2) = 0

(x - 2) is common so

(2x - 1)(x - 2) = 0
and 2x - 1 = 0 or x - 2 = 0  and now you can find x.

The last example is solved in the same way.

All points to the left of zero on a horizontal number line are negative. a number line is a picture of a graduated straight line that serves as abstraction for real numbers. this number line can be extended to the left to represent numbers which are smaller than 0. such numbers are called negative numbersmark me brainliest