Sum of two algebraic expressions is addition of two expressions. The sum of the given expressions is given as: Option B: $2.8x + 8.7$

<h3>What are like terms?</h3>

Those terms which have same variables raised with same powers.

For example, $5x^3$ and $3x^3$ are like terms since variable is same, and it is raised to same power 3.

For example $5x^2$ and $x^3$ are not like terms as the variables are same but powers aren't same.

<h3>What are coefficients?</h3>

Constants who are in multiplication with variables are called coefficients of those variables.

For example, in $10x^2$ we have 10 as coefficient of $x^2$

<h3>When can we add or subtract terms of polynomial by their coefficient's addition or subtraction?</h3>

Suppose we have $5x^2 + 6y$

Since those terms are not like terms, their coefficient won't be add and the expression we've got right now, is its simplest form and cannot be reduced more.

If we have, suppose,

$4x + 5x^2 + 2x$ , then we see that 4x and 2x are like terms, their coefficient can be added and thus, the simplified form would be

$(4+2)x + 5x^2 = 6x + 5x^2$

For the given condition, the needed sum is evaluated as:

$(-2.1x + 3.7) + (5 + 4.9x) = (-2.1 + 4.9)x + 5 + 3.7 = 2.8x + 8.7$

Thus,

The sum of the given expressions is given as: Option B: $2.8x + 8.7$

Learn more about addition of polynomials:

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