Question

Dr fungsi f dan g diketahui f(x) = 2x2+3x-5 dan g (x) = 3x-2 agar (g o f ) (a) = 11 nilai a yg positif adalah. ..

Answer 1

(g o f) (a) = g.f(a)
11 = (3a-2) . (2a²+3a-5)
11 = 6a²+9a²-15a-4a²-6a+10
11 = 11a²-21a+10
11a²-21a+10-11 = 0
11a²-21a-1 = 0

Answer 2

F(x) = 2x² + 3x - 5
g(x) = 3x - 2
(g o f) (x) = g (f(x)) = 3(2x² +3x - 5) - 2
                           = 6x² + 9x - 15 - 2
                           = 6x² + 9x - 17
(g o f) (a) = 11
6a² + 9a - 17 = 11
6a² + 9a - 28 = 0
 
D = b² - 4ac = 9² - 4·6·28 = - 581
D<0 maka akar-akarnya imajiner, nilai a imajiner