Question

How do you evaluate the following expression when x = 3 and y = 4 for \[3{{x}^{2}}\]?

Answer 1

Hint: Consider the given expression \[3{{x}^{2}}\] and substitute the given values of x and y to get the answer. Leave the value of y as it is, it does not affect the value of the expression \[3{{x}^{2}}\]. To evaluate \[{{x}^{2}}\], multiply x two times after substituting x = 3.

Complete answer:
Here, we have been provided with the expression \[3{{x}^{2}}\] and we are asked to evaluate it at x = 3 and y = 4. That means we have to substitute x = 3 and y = 4 in the given expression and determine its value.
Now, as we can see that the given expression \[3{{x}^{2}}\] has only one variable, i.e., x, and there are no terms of y. That means the value of y will have no effect on the value of the expression. Therefore, we can say that the value of the expression depends on only one variable, that is x. Substituting the given value of x, i.e., x = 3 in the provided expression, we get,
\[\Rightarrow E=3\times {{3}^{2}}\]
Here, we have assumed the value of the expression \[3{{x}^{2}}\] equal to E. As we can see that the exponent of 3 is 2, that means we have to multiply 3 two times, so we have,
\[\begin{align}
  & \Rightarrow E=3\times \left( 3\times 3 \right) \\
 & \Rightarrow E=3\times 9 \\
 & \Rightarrow E=27 \\
\end{align}\]
Hence, the value of the expression \[3{{x}^{2}}\] at x = 3 and y = 4 is 27.

Note: One may not get confused that if y = 4 has no use in the calculation then why is it provided in the question. Sometimes we are provided with certain values of variables which have no use. This is done to make us think that we are making the wrong solution. So, you must read the question carefully before solving it. If the variable y would have been present in the expression then only y = 4 would have affected the answer that we have obtained.