At what value of the variable the value of the expression 8y (y -7) is 15 more than the value of the expression 2y (4y -10.5).

In order to find at what value of the y variable the value of the expression 8y (y – 7) is 15 more than the value of the expression 2y (4y – 10.5), we will compose and solve a linear equation.

8y (y – 7) – 15 = 2y (4y – 10.5);

Let’s open the brackets on both sides of the equation:

8y * y – 8y * 7 – 15 = 2y * 4y – 2y * 10.5;

8y ^ 2 – 56y – 15 = 8y ^ 2 – 21y;

We pass to the grouping of terms with and without variables in different parts of the equation:

8y ^ 2 – 56y – 8y ^ 2 + 21y = 15;

y (21 – 56) = 15;

-35y = 15;

y = 15: (-35);

y = -3/7.

Answer: y = -3/7.