Step-by-step explanation:
By binomial theorem,
T(r+1) = nCr * a^(r+1) * b^r
Term 4 = 7C3 * (2x)^4 * (-5y)^3 = 35 * (16x^4) * (-125y^3) = -70000x^4y^3.
Answer: 3.6 feet per year
Pick any column and divide the feet over the years
eg: 7.2/2 = 3.6 (column 1)
You can think of it as the ratio
7.2 feet: 2 years
and then divide both sides by 2 to get "1 year" on the right side
7.2 feet: 2 years
7.2/2 feet: 2/2 years
3.6 feet: 1 year
To solve divide both sides by 4 to cancel out the 4 on the x side to get x alone. Then just do -10/4. That gives you 2.5 so (X=2.5). Hope I helped and have a great day and night
