The length plus the width of a rectangle is 10 . let x represent the length. the equation for the area y of the rectangle is y = x(10 – x). the y-value of the vertex gives the (maximum or minimum) value of the (length or area or width)of the rectangle

maximum value of the area of the rectangle is 25 units^2.

Step-by-step explanation:

Let x represent the length of the rectangle.  Then the width must be w = 10 - x.

Thus we have an equation for the area (x(10 - x)) = y of the rectangle.

Expanding this by performing the indicated multiplication, we get the area formula y = x(10 - x), or y = -x^2 + 10x + 0.

The coefficients of the x terms of this quadratic are {-1, 10, 0}.

The vertex is at x = -b/(2a), which here is x = -10/(2*-1), or x = 5.

The y value, representing the area of the rectangle, is y = x(10 - x), or, in this particular case, y = 5(10 - 5), or y = 25.  This is the maximum possible value of the area of the rectangle.

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.