Question

Diketahui f:x -> 2x+5 dan f(g(x))=13-2x. jika g(f(a²+1))= 5a - 6, nilai a sama dengan..... a.-1 &6. b.-1/2 & 3. c. 1/2 dan -3 d.1/2 & 3/2. e.1 dan 5

Answer 1

F(x) = 2x + 5
f {g(x)}= 13 - 2x
2. g(x)+5 = 13 - 2x
2. g(x)= 13 - 5 - 2x = 8 - 2x
g(x)= 1/2 (8-2x)
g(x)= 4 - x

g{ f(a²+1)} = 5a - 6
4 - f(a²+1) = 5a - 6
4 - { 2(a²+1) +5) = 5a - 6
4 - 2(a²+1) - 5 = 5a - 6
4 - 2a² -2 - 5 = 5a-6
-2a² -3 = 5a - 6
-2a² -5a -3 + 6 = 0
-2a² - 5a + 3 = 0
atau
2a² +5a -3 = 0
(2a -1)(a+3)= 0
a = 1/2  atau a = - 3