Rewrite the first fraction using the LCD of 7 and 21.

the lcd of 7 and 21 is 21

Step-by-step explanation:

You need to know the least common denominator (LCD) of 21 and 7 if you want to add or subtract two fractions with 21 and 7 as denominators.

The least common denominator, also called lowest common denominator (LCD), of 21 and 7 is 21.

Here is a math problem example where you need to know the LCD of 21 and 7 to solve:

3/21 + 2/7 = ?

Step 1) Take the LCD and divide each denominator by it as follows:

21/21 = 1

21/7 = 3

Step 2) Multiply each nominator with the respective answers from Step 1:

3 x 1 = 3

2 x 3 = 6

Step 3) Put it all together to solve the problem:

3/21 + 6/21 = 9/21

= 3/21 + 2/7 = 9/21

It's that easy! Once again, the lowest common denominator (LCD) of 21 and 7 is as follows:

21

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this