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Length = √area = √81 = 9
diagonal = √2 * side = √2*9 = 9√2
Answer:
11 years old
Step-by-step explanation:
If four brothers have the average age 6, then the sum of their ages is

years.
Let x years be the age of sister. If four brothers and their sister have the average age 7, then

Multiply this equation by 5:

The sister is 11 years old.
y- intercept = (0, 4), x-intercept = (- 2, 0)
to find the intercepts let x = 0 and y = 0 in the equation
x = 0 → y = 0 + 4 =4 ⇒ y-intercept (0, 4)
y = 0 → 2x + 4 = 0 ⇒ x = - 2 ⇒ x- intercept(- 2, 0)