Find a and b.

$4x^{3}-ax^{2}-bx+18$
→Given x+2 is a factor
→Now,putting x=-2 in the polynomial.
$4×(-2)^{3}-a×(-2)^{2}-b×(-2)+18=0$
● $b-2a=7.......(1)$
→By Vieta's Formula
■ $\alpha$ + $\beta$ + $\gamma$ = $\frac{a}{4}$
■ $\alpha$ × $\beta$ × $\gamma$ = $\frac{-18}{4}$
→Given two zeroes equal and one zero -2
● $\alpha$ + $2\beta$ = $\frac{a}{4}$
● $-2$ + $2\beta$ = $\frac{a}{4}$
● $\beta$ = $\frac{a+8}{8}......(2)$
● $\alpha$ × $\beta^{2}$ = $\frac{-18}{4}$
● $-2$ × $\beta^{2}$ = $\frac{-9}{2}$
● $\beta$ = $\frac{3}{2}.....(3)$
→Now equating (2) and(3).
● $\frac{a+8}{8}$ = $\frac{3}{2}$
● $a$ = $4$
→Now putting value of 'a' in (1).
● $b-2a=7$
● $b=15$
● $a×b=4×15$
● $a×b$ = $\boxed{60}$