Respuesta :
Answer: 1) C. (x+3)(x+7)
2) D. (x-3)(x-8)
3) C. (x-2)(x+4)
5) B. (x+9)(x-9)
Step-by-step explanation:
1)
x2 + 10x + 21
(we look for 2 numbers whose product gives 21 and whose sum gives 10, then replace 10x by those two numbers)
x2 + 7x + 3x +21
x(x+7) + 3(x+7)
(x+3)(x+7)
2)
x2 - 11x + 24
(we look for 2 numbers whose product gives 24 and whose sum gives -11, then replace -11x by those two numbers)
x2 -3x-8x +24
x(x-3) -8(x-3)
(x-3)(x-8)
3)
x2 + 2x - 8
(we look for 2 numbers whose product gives -8 and whose sum gives 2, then replace 2x by those two numbers)
x2 + 2x - 8
x2 + 4x - 2x - 8
x(x+4) -2(x+4)
(x+4)(x-2)
5)
x2 - 81
Its a difference of two squares
(x-9)(x+9)