Question

If a = 5 and b=2 then find the value of - 2ab and - 3a+b

Answer 1

-2ab = -2(5)(2) = -20
-3a+b = -3(5)+2 = -13

Answer 2

• -2ab = -20
• -3a + b = -13

Concept:

Here, we need to understand the idea of evaluation.

When encountering questions that gave you an expression with variables, then stated: "If x = a, y = b, z = c" (a, b, c are all constants), this means you should substitute the value given for each variable back to the expression.

Solve:

PART I: Find the value of -2ab

Given information

a = 5

b = 2

Given expression

-2ab

Substitute values into the expression

-2 (5) (2)

Simplify by multiplication

=-10 (2)

=
`\boxed{-20}`

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PART II: Find the value of -3a + b

Given information

a = 5

b = 2

Given expression

-3a + b

Substitute values into the expression

-3 (5) + (2)

SImplify by multiplication

=-15 + (2)

Simplify by addition

=
`\boxed{-13}`

Hope this helps!! :)

Please let me know if you have any questions