The work of a student to find the dimensions of a rectangle of area 8 + 16x and width 4 is shown below: Step 1: 8 + 16x
Step 2: 4(4) + 4(12x)
Step 3: 4(4 + 12x)
Step 4: Dimensions of the rectangle are 4 and 4 + 12x

In which step did the student first make an error and what is the correct step?

answer: c, the green line

step-by-step explanation:

there is no black line, eliminate b.

simple interest implies periodic payments, but the red line shows no payments, eliminate d.

simple interest has equal payments. if paid say every day, the graph is about a straight line (actually a stairstep).

the yellow line is not straight, eliminate a.

check: the green line is straight, answer is c.

simple interest with positive interest rate gives a straight line sloping up to the right. green line:

g(t) = $100 + ($200-$100) ÷ (20 years) × (t years)

= $100 + (4%/year) × ($100)(t years)

incidentally, the yellow line curving upward represents continuously compounded interest

y = $100 × 2^(t years / (14 assuming the yellow line hits $200 at 14 years. 2^0 is 1, so y(0) = $100; 2^(14/14) is 2, so y(14) = $200.

b

step-by-step explanation: