First you want to reduce the brackets
Next you want to factor out the common number 3
Next you want to factor 20 + x^3 + 11x - 8x^2 by using the polynomial division method/technique
Lastly you just factor x^2 - 9x + 20 to get the answer.
Yes you are correct, the solutions are 1, 4, and 5.
For these problems you have to use PEMDAS so for problem 15 you would do the parentheses first, (21-3) you get 18 and then exponents, 3^2, you get 9, no multiplication but there is division so take your answers, 18 and 9 and divide them, you get 2, so the answer to 15 is 2.
3(x-5)-4(x+3)
Multiply the first bracket by 3
(3)(x)=3x
(3)(-5)=-15
(-4)(x)=-4x
(-4)(3)=-12
3x-15-4x-12
3x-4x-15-12 ( combine like terms)
Answer: -x-27