Question

3 what is the value of the expression below when c = 5 and d = 4? $6c^2 - 5d + 8$ a 79 b 888 c 48 d 138

Explanation:

Step1: Substitute \( c = 5 \) and \( d = 4 \) into the expression.

We get \( 6\times(5)^2 - 5\times4 + 8 \).

Step2: Calculate the exponent.

\( (5)^2 = 25 \), so the expression becomes \( 6\times25 - 5\times4 + 8 \).

Step3: Perform the multiplications.

\( 6\times25 = 150 \) and \( 5\times4 = 20 \), so now we have \( 150 - 20 + 8 \).

Step4: Perform the subtraction and addition.

First, \( 150 - 20 = 130 \), then \( 130 + 8 = 138 \). Wait, no, wait, let's recalculate: \( 6\times25 = 150 \), \( 5\times4 = 20 \), so \( 150 - 20 = 130 \), then \( 130 + 8 = 138 \)? Wait, no, wait the original expression is \( 6c^2 - 5d + 8 \). Wait, \( c = 5 \), so \( c^2 = 25 \), \( 6\times25 = 150 \), \( 5d = 5\times4 = 20 \), so \( 150 - 20 + 8 = 138 \)? But wait, option A is 79, did I make a mistake? Wait, no, wait \( 6\times25 = 150 \), \( 150 - 20 = 130 \), \( 130 + 8 = 138 \)? But the options are A.79, B.888, C.48, D.138. Wait, maybe I miscalculated. Wait, no, let's check again. \( 6c^2 \) when \( c = 5 \) is \( 6\times25 = 150 \), \( -5d \) when \( d = 4 \) is \( -20 \), then \( +8 \). So \( 150 - 20 + 8 = 138 \). So the answer should be D? Wait, but let me check again. Wait, maybe the expression is \( 6c^2 - 5d + 8 \). Wait, \( c = 5 \), so \( 6(5)^2 = 625 = 150 \), \( 5d = 20 \), so \( 150 - 20 = 130 \), \( 130 + 8 = 138 \). So the correct answer is D.138? Wait, but maybe I made a mistake. Wait, no, let's recalculate: \( 6\times25 = 150 \), \( 5\times4 = 20 \), \( 150 - 20 = 130 \), \( 130 + 8 = 138 \). So the answer is D.138.

Answer:

D. 138