Using factorization method;
x²+13x+40=0
x²+13+40
Find two numbers that you can add together to give the co-efficient of variable x. (I.e 13 for this question). Also, you'll find two numbers that you can multiply with each other to give you the whole number as an answer. (I.e 40 in this question). The two numbers must be the same (i.e the two numbers that will be added to give the co-efficient of x and the two numbers that will be multiplied to give the whole number must be the same two).
The two numbers are +5 and +8
The equation will therefore be = x²+5x+8x+40
You'll then factorize (I.e use a common factor of both values to bracket them)
x(x+5)+8(x+5)
(x+8)(x+5)
x is therefore (x+8=0) or (x+5=0)
x=(x=0-8) or (x=0-5)
x= -8 or x= -5
