SOLUTION: A baby weighs 9 pounds at birth and 30 pounds at age 3. Write an equation that shows the linear relationship between the weight and age. How much the child will weigh at age 12

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A baby weighs 9 pounds at birth and 30 pounds at age 3. Write an equation that shows the linear relationship between the weight and age. How much the child will weigh at age 12      Log On


   

Question 819718: A baby weighs 9 pounds at birth and 30 pounds at age 3. Write an equation that
shows the linear relationship between the weight and age. How much the child
will weigh at age 12?
Can you make sure to explain the steps as well? I need this to study for my final on Wed. Thank you!!
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You have to decide which variable to
plot on which axis.
-----------------
The independent variable goes on the x-axis
That would be the age.
-----------------
The dependent variable, pounds, goes on the y-axis
because the pounds on the age.
------------------
Now you can say:
+y+=+f%28x%29+, and you can use the general
point-slope formula to show the relation
+%28+30+-+9+%29+%2F+%28+3+-+0+%29+=+%28+y+-+9+%29+%2F+%28+x+-+0+%29+
+21%2F3+=+%28+y-9+%29+%2F+x+
+7x+=+y+-+9+
+y+=+7x+%2B+9+
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How much will the child weigh at age 12?
+y+=+7%2A12+%2B+9+
+y+=+84+%2B+9+
+y+=+93+ pounds
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check the equation:
When child is born:
+y+=+7%2A0+%2B+9+
+y+=+9+
OK
When child is 3:
+y+=+7%2A3+%2B+9+
+y+=+21+%2B+9+
+y+=+30+
OK