Answer:

Step-by-step explanation:
Given
← factorise numerator and denominator
2x² - 18 ( factor out 2 from each term )
= 2(x² - 9) ← difference of 2 squares
= 2(x - 3)(x + 3)
and
x² + 4x - 21 = (x + 7)(x - 3) , then
=
← cancel common factor (x - 3) on numerator/ denominator
= 
hi
u0 = 64 with u(n+1) = un *0.75
u3 = 64 *0.75^3 = 27
sum is : 64 * ( 0.75^4 -1) / 0.75-1 = 175
manual proof : 64 + 48+36+27 = 175
X(x+2) = 48
x^2 + 2x = 48
x^2 + 2x - 48 = 0
*Use quadratic formulae*
x = 6
Numbers are 6 and 8