Question

-2 a -2b при а= 4/5,b 1/4

Answer 1

Ответ:

-2×4/5=-1,6

-2×1/4=-0,5

-1,6-(-0,5)=-2,1

Answer 2

Решение и ответ:

-2a - 2b, при а = 4/5; b = 1/4

1 способ

$\displaystyle-2a-2b=-2(a+b)=-2\left({\frac{4}{5}+\frac{1}{4}}\right)=-2\left({\frac{{16}}{{20}}+\frac{5}{{20}}}\right)=-2\cdot\frac{{21}}{{20}}=\frac{{-21}}{{10}}=-2\frac{1}{{10}}=-2.1$

2 способ

$\displaystyle-2a-2b=-2\cdot\frac{4}{5}-2\cdot\frac{1}{4}=-\frac{8}{5}-\frac{1}{2}=-\frac{{16}}{{10}}-\frac{5}{{10}}=\frac{{-16-5}}{{10}}=\frac{{-21}}{{10}}=-2\frac{1}{{10}}=-2.1$

Answer 3

To find the value of the expression -2a - 2b when a = 4/5 and b = 1/4, we substitute these values into the expression and perform the calculations:

-2(4/5) - 2(1/4)

First, let's simplify the expression within the parentheses:

-2(4/5) = -8/5 -2(1/4) = -2/4 = -1/2

Now we substitute the simplified values back into the expression:

-8/5 - 1/2

To add or subtract fractions, we need a common denominator. The least common denominator (LCD) for 5 and 2 is 10:

(-8/5)(2/2) - (1/2)(5/5) = -16/10 - 5/10 = (-16 - 5) / 10 = -21/10

Therefore, when a = 4/5 and b = 1/4, the value of -2a - 2b is -21/10.