Question

Simplify and find the value \[2-4x+5x-9\] when \[x=5\].

Answer 1

Hint: We are given with a linear expression. In order to solve this linear expression, firstly we will be solving the variable and constant terms and express it in the form of one variable and one constant form. After this, we will be substituting the given value \[x=5\] in the obtained expression and compute it. This will be our required answer.

Complete step by step answer:
Now let us have a brief regarding the linear expressions. A linear expression is an expression whose degree is one. It can have a number of terms as per requirement. An expression with \[=\] symbol is termed as an equation. We can solve both the equation and expression for the value of the variable and that would be the solution of particular expression. The general form of a linear expression is \[ax+b\] .
Now let us find the of \[2-4x+5x-9\] when \[x=5\].
Firstly, we will be solving the variable terms and the constant terms as they can be simplified further.
Now consider, \[2-4x+5x-9\]
\[\Rightarrow x-7\]
Now, let us substitute \[x=5\] in \[x-7\].
\[\Rightarrow x-7=5-7=-2\]
\[\therefore \] The value of \[2-4x+5x-9\] when \[x=5\] is \[-2\].

Note: We can apply linear expressions to find the relationship between the variable and constant. We can also use them in word solving problems. We can apply them in finding simple interests, motions and many more.
This problem can also be solved without simplifying the like terms in the expression as shown below.
\[\begin{align}
  & \Rightarrow 2-4x+5x-9 \\
 & \Rightarrow 2-4\left( 5 \right)+5\left( 5 \right)-9 \\
 & \Rightarrow 2-20+25-9 \\
 & \Rightarrow -29+27 \\
 & =-2 \\
\end{align}\]
Hence, we can observe that we have obtained the same value.
So any of the methods can be followed.