Jika 9x-¹=(⅓)⁴x-¹, maka F(y)=y²+2x y+4x² Mempunyai nilai minimum ...

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9ˣ⁻¹  = (1/3)⁴ˣ⁻¹
3²⁽ˣ⁻¹) = (3⁻¹)⁴ˣ⁻¹
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2(x - 1) = - 1(4x - 1)
2x - 2 = -4x + 1
6x = 3
x= 1/2

f(y) = y² + 2xy + 4x²
untuk x = 1/2
f(y)= y² + 2(1/2)y + 4(1/2)²
f(y)= y² + y + 1
nilai minimum
jika f '(y) = 0
2y + 1=  0
y = - 1/2

f(- 1/2) = (-1/2)² + (-1/2) + 1
f(-1/2) = 1/4 - 1/2 + 1
f(-1/2) = 3/4

nilai minmum = 3/4