Question

1. evaluate the expression ( ab - 2(ab + a^2) + 3a^2 ) when ( a = 5 ) and ( b = -4 ).

( \bigcirc ) 45

( \bigcirc ) 136

( \bigcirc ) 145

( \bigcirc ) (a circled check mark)

Explanation:

Step1: Simplify the expression

First, expand the brackets:
\( ab - 2(ab + a^2) + 3a^2 = ab - 2ab - 2a^2 + 3a^2 \)
Then, combine like terms:
\( (ab - 2ab) + (-2a^2 + 3a^2) = -ab + a^2 \)

Step2: Substitute \( a = 5 \) and \( b = -4 \)

Substitute the values into the simplified expression \( -ab + a^2 \):
\( - (5)(-4) + (5)^2 \)

Step3: Calculate each term

Calculate \( - (5)(-4) \): \( - (5)(-4) = 20 \)
Calculate \( (5)^2 \): \( (5)^2 = 25 \)

Step4: Add the results

Add the two terms: \( 20 + 25 = 45 \)

Answer:

45