Question

A=3x+7 B=2x^2-1 C=7x^2-3x Find: A+B+C= A-B-C=

Answer 1

Given the equations:

`A=3x+7`
`B=2x^2-1`
`C=7x^2-3x`

• You need to add them in order to find:

`A+B+C`

Set p that:

`A+B+C=(3x+7)+(2x^2-1)+(7x^2-3x)`

Remember the Sign Rules for Multiplication:

`\begin{gathered} +\cdot+=+ \\ -\cdot-=+ \\ +\cdot-=- \\ -\cdot+=- \end{gathered}`

Then, you know that the positive signs between the parentheses do not change the signs inside of them:

`A+B+C=3x+7+2x^2-1+7x^2-3x`

Combine the like terms (these are defined as those terms that have the same variables with the same exponents). Then:

`A+B+C=9x^2+6`

• Subtract the equations in order to find:

`A-B-C`

Set up that:

`A-B-C=(3x+7)-(2x^2-1)-(7x^2-3x)`

Simplify it by distributing the negative signs and then combining the like terms:

`A-B-C=3x+7-2x^2+1-7x^2+3x`
`A-B-C=-9x^2+6x+8`

Hence, the answer is:

`A+B+C=9x^2+6`
`A-B-C=-9x^2+6x+8`