Chapter 8.2, Problem 19GP

To determine

The solution of the equation $-4=8y-9y+6$ , and check the solution.

Answer to Problem 19GP

  $y=10$

Explanation of Solution

Given:

The equation, $-4=8y-9y+6$ .

Concept Used:

• To get rid of a number in addition from one side, subtract the same number from both sides of equal sign.
• To get rid of a number in subtraction from one side, add the same number both sides of equal sign.
• To get rid of a number in multiplication from one side, divide the same number from both sides of equal sign.
• To get rid of a number in division from one side, multiply the same number both sides of equal sign.

Rules of Addition/ Subtraction:

• Two numbers with similar sign always get added and the resulting number will carry the similar sign.
• Two numbers with opposite signs always get subtracted and the resulting number will carry the sign of larger number.

Rules of Multiplication/ Division:

• The product/quotient of two similar sign numbers is always positive.
• The product/quotient of two numbers with opposite signs is always negative.

Calculation:

In order to solve the given equation $-4=8y-9y+6$ for the unknown variable, isolate the variable term y on one side by performing some basic algebraic operations to get rid of the other numbers and terms associated with it.

Here to isolate y on right side, first combining both the y terms and then subtract 6 from both sides and then divide both sides by -1 and then simplify further as shown below,

  $\begin{array}{l}-4=8y-9y+6\\ -4=-y+6\\ -4-6=-y+6-6\\ -10=-y\\ \frac{-10}{-1}=\frac{-y}{-1}\\ 10=y\end{array}$

Thus, the solution of the given equation is $y=10$ .

Now, to check the solution, substitute $y=10$ in the given equation and check whether the values on both sides of equal sign is same or no. So, it gives

  $\begin{array}{l}-4=8y-9y+6\\ -4=8\left(10\right)-9\left(10\right)+6\\ -4=80-90+6\\ -4=-4\text{True Statement}\end{array}$

Since, the left hand side and right hand side are equal, so the solution is correct.