Lilly took out an 80/20 mortgage to buy a house costing $100,000. the first
(80%) mortgage has an interest rate of 4.75%, and the second (20%)
mortgage has an interest rate of 7.525%. both the first mortgage and the
second mortgage are 30-year fixed-rate mortgages. what is her monthly
payment on the first mortgage?

$442.1 per month

Step-by-step explanation:

Lilly took 80/20 mortgage to buy house costing $ 100000

80% × 100000 = 80000 for the first at 4.75%

80000 × 4.75% = 80000 × 0.0475 = $ 3800 as interest per year,

20% × 100000 =  20000 for the second mortgage

20000 × 7.525% = 20000 × 0.07525 = 1505 as interest per year

add the first interest and the second interest

3800 + 1505 = 5305

divide the answer by 12 months to find the monthly payment

5305 / 12 = $442.1 per month

the graph in the attached figure

step-by-step explanation:

we have

using a graphing tool

the graph in the attached figure

the roots are ( x-intercepts) x=-0.5,x=1,x=3

the y-intercept is the point (0,3)