Question

(5-а)(5+а)-а(20-а) при а= -19/20

Answer 1

Ответ:44

Объяснение:25-а²-20а+а²=25-20а

25-20*(-19/20)=25+19=44

Answer 2

To evaluate the expression (5-а)(5+а)-а(20-а) with а = -19/20, we substitute the given value of а into the expression:

(5 - (-19/20))(5 + (-19/20)) - (-19/20)(20 - (-19/20))

To simplify this expression, we need to perform the arithmetic operations:

First, let's simplify the individual terms:

(5 - (-19/20)) = 5 + 19/20 = 100/20 + 19/20 = 119/20

(5 + (-19/20)) = 5 - 19/20 = 100/20 - 19/20 = 81/20

(20 - (-19/20)) = 20 + 19/20 = 400/20 + 19/20 = 419/20

Now, let's substitute these values back into the expression:

(119/20)(81/20) - (-19/20)(419/20)

To multiply fractions, we multiply the numerators together and the denominators together:

(119 * 81) / (20 * 20) - (-19 * 419) / (20 * 20)

Now, we simplify further:

(9639/400) - ( - 7939/400)

To subtract fractions, we need a common denominator:

(9639 - (-7939))/400

Simplifying the numerator:

(9639 + 7939)/400 = 17578/400

Finally, we can simplify this fraction:

17578/400 = 43945/1000 = 43.945

Therefore, when а = -19/20, the expression (5-а)(5+а)-а(20-а) evaluates to 43.945.