What is the answer to 3x^2 + 30x+75

The answer is 3 (x+5) ^2

Factor out 3 from the original equation

3 (x^2+10x+25)

Then find two numbers that multiply to give 25 and add to give 10. The two numbers are 5 and 5

This gives ...

3 (x^2+5x+5x+25)

Factorise the expression in the brackets

3 (x+5) (x+5)

Combine like terms

3 (x+5) ^2