7. misalkan 2x+6 = a a² - 2a - 8 = 0 (a-4)(a+2)= 0 a = 4 --> 2x + 6 = 4 --> 2x = 4-6 = -2 --> x = -1 a = -2 --> 2x+6 = -2 --> 2x =-2-6 = - 8 --> x = -4 HP (-4, -1)
8. a = 1 , b = -2m, c = 8m x1+x2 = -b/a = 2m x1 x2 = c/a = 8m misal p = a^2+b^2 + ab p = (a+b)^2 - 2ab + ab p= (a+b)^2 - ab p= (2m)^2 - 8m p = 4m^2 - 8m p minimum jika m = -b/2a = -(-8)/ {2(4)} = 8/8 = 1
b^2 - 4ac = 0
(-4/3)^2 - 4(1)(c) = 0
16/9 - 4c = 0
c = 16/9 : 4 = 4/9
7. misalkan 2x+6 = a
a² - 2a - 8 = 0
(a-4)(a+2)= 0
a = 4 --> 2x + 6 = 4 --> 2x = 4-6 = -2 --> x = -1
a = -2 --> 2x+6 = -2 --> 2x =-2-6 = - 8 --> x = -4
HP (-4, -1)
8. a = 1 , b = -2m, c = 8m
x1+x2 = -b/a = 2m
x1 x2 = c/a = 8m
misal p = a^2+b^2 + ab
p = (a+b)^2 - 2ab + ab
p= (a+b)^2 - ab
p= (2m)^2 - 8m
p = 4m^2 - 8m
p minimum jika m = -b/2a = -(-8)/ {2(4)} = 8/8 = 1