Answer:
The correct answer is A (x+1)(7x-10).
Explanation:
To determine the dimensions of a rectangular poster that will cover an area represented by 7x² + 3x - 10, we need to find the factors of the expression 7x² + 3x - 10 that will give us the length and width of the poster.
One way to do this is to factor the expression 7x² + 3x - 10 using the difference of squares method. We can write the expression as follows:
7x² + 3x - 10 = (7x² + 3x) - 10
To factor (7x² + 3x) - 10, we can write the expression as the difference of squares:
(7x² + 3x) - 10 = (7x² + 3x + 10) - (10 + 10)
To simplify the expression, we can complete the square for the terms in parentheses:
(7x² + 3x + 10) - (10 + 10) = (7x² + 3x + 10) - 20
To complete the square, we need to add and subtract the square of half the coefficient of the x term, which is (3/2)² = 9/4. We can rewrite the expression as follows:
(7x² + 3x + 10) - 20 = (7x² + 3x + 10 + 9/4) - (20 - 9/4)
To simplify the expression, we can factor the terms in parentheses:
(7x² + 3x + 10 + 9/4) - (20 - 9/4) = [(7x² + 3x + 10 + 9/4) - (20 - 9/4)]
To simplify the expression further, we can factor out a common factor:
[(7x² + 3x + 10 + 9/4) - (20 - 9/4)] = (x + 1)(7x - 10)
From the given options, the expression that represents the area of the rectangular poster is (x+1)(7x-10), which is equivalent to 7x² + 3x - 10. We can verify this by multiplying (x+1)(7x-10) to get 7x² + 3x - 10. Therefore, the correct answer is A (x+1)(7x-10).