The first one is a perfect square and can be factored as such by taking the square root of both terms. Square root of 49 is +/-7. Square root of x^2 is x
(x+7)(x-7)
Roots are 7 and -7
The others we can do the same way only they are not perfect squares so we just need to take the square root of both terms.
Square root of b^2 is b. Square root of 18 can be written as 3√2
Roots are +3√2 and -3√2
Same for the third problem. Square root of z^2 is z. Square root of 13 is already in it's simplist form as √13
Roots are +√13 and -√13