Respuesta :

I'm assuming that you meant: 
y = 7x² + 3 

Remember! Inputs are always x values (unless stated otherwise). Meaning the problem says: 
x = 4 

y = 7(4)² + 3 

The square only applies to the 4. The 7 is not going to be squared! (To be exact it only applies to whatever the value of x is. 

4² = 4·4 = 16

Remember: 
Parenthesis
Exponents
Multiplication
Division
Addition
Subtraction

Follow PEMDAS from left to right (or in the case above from top to bottom).

7·16 + 3 = ? 

16·7 = 10·7 + 6·7 = 70 + 42 = 112
(All I did to multiply was break it up into parts. If it confuses you don't worry about it, and just multiply it out like normal or use a calculator if you are allowed to)

112 + 3 = ? 

Our output is: 
115!

If the input of the function is 4, the output will be 115

Given the function y = 7x^2 + 3

The input variale is x

The output variable is y

If the input is 4, we will substitute x = 4 into the function and get y

y = 7(4)² + 3

y = 7(16) + 3

y = 112 + 3

y = 115

Hence if the input of the function is 4, the output will be 115

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