If a = -4 and b = 3, what is the value of the expression 3a^2 - 2ab? — ACT

If $a = -4$ and $b = 3$ , what is the value of the expression $3a^2 - 2ab$ ?

Substituting

a = -4

and

b = 3

yields

3(-4)^2 - 2(-4)(3) = 3(16) - (-24) = 48 + 24 = 72

Substitute the given values into the expression

Replace

a

with

-4

and

b

with

3

3a^2 - 2ab

to get

3(-4)^2 - 2(-4)(3)

Direct substitution of known variable values.

Evaluate the exponent

(-4)^2 = 16

, so the term

3(-4)^2

becomes

3(16) = 48

Exponents must be evaluated before multiplication according to PEMDAS.

Evaluate the second multiplication term

2ab = 2(-4)(3) = -24

Multiply the numerical factors together.

Subtract the terms to find the final value

48 - (-24) = 48 + 24 = 72

Subtracting a negative number is equivalent to adding its positive value.

Evaluating Algebraic Expressions with Negative Values

Estimated Time:45s

Question