jika a+1=b+2=c+3=d+4=a+b+c+d+5 jadi berapakah a+b+c+d.?

a + 1 = b + 2 = c + 3 = d + 4 = a + b + c + d + 5

maka :
a + 1 = b + 2
a = b + 1 .. (1)

b + 2 = c + 3
c = b - 1 ... (2)

b + 2 = d + 4
d = b - 2 ...(3)

d + 4 = a + b + c + d + 5
a + b + c = -1 ..(4)

subtitusikan nilai a dan c ke (4), didapat :
a + b + c = -1
(b + 1) + b + (b - 1) = -1
b + 1 + b + b - 1 = -1
3b = -1
b = -1/3

maka, nilai b adalah -1/3

subtitusikan nilai b ke (1), (2) dan (3). didapat :
a = b + 1 = (-1/3) + 1 = 2/3
c = b - 1 = (-1/3) - 1 = -4/3
d = b - 2 = (-1/3) - 2 = -7/3

maka, nilai dari a + b + c + d = (-1/3) + (2/3) + (-4/3) + (-7/3) = -10/3

jadi, nilai dari a + b + c + d adalah -10/3