Answer:
See Explanation
Step-by-step explanation:
[tex]f(x) = 4 - 6x + 3 {x}^{2}...(1) \\ plug \: x = a \: in \: (1) \\ f(a) = \boxed{ 4 - 6a + 3 {a}^{2} } \\ \\ next \: plug \: x = (a + h) \: in \: (1) \\ f(a + h) = 4 - 6(a + h) + 3 {(a + h)}^{2} \\ = 4 - 6a - 6h + 3( {a}^{2} + {h}^{2} + 2ah) \\ = 4 - 6a - 6h + 3 {a}^{2} + 3{h}^{2} + 6ah \\ f(a + h) = \boxed{3 {a}^{2} + 3{h}^{2} + 6ah - 6a - 6h + 4} \\ \\ now \\ \\ \frac{f(a + h) - f(a)}{h} \\ \\ = \frac{(3 {a}^{2} + 3{h}^{2} + 6ah - 6a - 6h + 4) -(4 - 6a + 3 {a}^{2} ) }{h} \\ \\ = \frac{3 {a}^{2} + 3{h}^{2} + 6ah - 6a - 6h + 4 -4 + 6a - 3 {a}^{2} }{h} \\ \\ = \frac{ 3{h}^{2} + 6ah - 6h }{h} \\ \\ = \frac{3h( {h} + 2a - 2) }{h} \\ \\ \frac{f(a + h) - f(a)}{h} = \boxed{ 3( 2a + h - 2)}[/tex]
