Find the solutions to each quadratic by factoring

Question

x^2+3x-18=0

3x^2-9x=o

x^2-10x+21=0

5x^2+30x+45=0

Answer 1

what method have you learned?

They all look pretty straightforward,
in the last one, first divide each term by 5, then it is easy.

x^2+3x-18=0
what two numbers multiply to get -18 and add to get +3 ?

mmmh, how about 6 and -3
(x+6)(x-3) = 0 , (expand it to verify)
x = -6 or x = 3

etc.