Question

3) 2 (k-7)(k+5)-(k-5)-(k-7)(7+k), пpи k=-1/2​

Answer 1

Ответ:

-53/4

Пошаговое объяснение:

2 (k-7)(k+5)-(k-5)-(k-7)(7+k), пpи k=-1/2​

2 (-1/2​-7)(-1/2​+5)-(-1/2​-5)-(-1/2​-7)(7+-1/2​)=2(-15/2)*9/2-(-11/2)-(-15/2)*13/2 = -15*9/2+11/2+15/2*13/2 = -135/2+11/2+195/4 = -53/4

Answer 2

To evaluate the expression when k = -1/2, we substitute -1/2 into the expression:

2 (k - 7)(k + 5) - (k - 5) - (k - 7)(7 + k)

Let's calculate this step by step:

Step 1: Substitute k = -1/2

2((-1/2) - 7)((-1/2) + 5) - ((-1/2) - 5) - ((-1/2) - 7)(7 + (-1/2))

Step 2: Simplify the expression within the parentheses:

2(-15/2)(9/2) - (-11/2) - (-15/2)(15/2)

Step 3: Multiply the values inside the parentheses:

(-15/1)(9/2) = -135/2

(-15/2)(15/2) = -225/4

Step 4: Substitute the values back into the expression:

2(-135/2) - (-11/2) - (-225/4)

Step 5: Simplify the expression:

-270/2 + 11/2 - 225/4

-135 + 11/2 - 225/4

Step 6: Convert all fractions to a common denominator:

-135 + 11/2 - (225/4)(2/2)

-135 + 11/2 - 450/4

Step 7: Simplify further:

-135 + 11/2 - 112.5

Step 8: Combine like terms:

-135 - 112.5 + 11/2

Step 9: Convert the mixed number into an improper fraction:

-135 - 112.5 + 11/2 = -270/2 - 225/2 + 11/2

Step 10: Combine the fractions:

(-270 - 225 + 11)/2

Step 11: Perform the arithmetic:

(-484)/2

Step 12: Simplify the expression:

-242

Therefore, when k = -1/2, the expression 2(k - 7)(k + 5) - (k - 5) - (k - 7)(7 + k) evaluates to -242.