Question

Diketahui f(x) = ax2 + b. jika f(2b) - f(b) = 3, dan lim x→1 f(bx):x-1=2, maka a + b= ???

Answer 1

F(x) = ax² + b
f(2b) - f(b) = 3 --> {a(2b)²+b } - (a(b)² + b} = 3
4ab² + b - ab² - b = 3
3ab² = 3
ab² = 1

lim(x->1) f(bx) /(x-1) = 2
f(bx) : (x-1) = 2 --> f(b) = 2
ab² + b = 2
(1) + b = 2
b = 1
ab² = 1 --> a = 1
a+ b = 2