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Cedaric completed the square for the quadratic expression 5x2 - 40x + 15, as shown.Step 1: 5(x2 -8x + 3)Step 2: 5(x2- 8x + 16 - 16 + 3)Step 3: 5((x + 4)2 -16 + 3)Step 4: 5((x + 4)2 - 13)Step 5: 5(x + 4)2 - 65What mistake, if any, did Cedric make?

Cedaric completed the square for the quadratic expression 5x2 40x 15 as shownStep 1 5x2 8x 3Step 2 5x2 8x 16 16 3Step 3 5x 42 16 3Step 4 5x 42 13Step 5 5x 42 65 class=
Cedaric completed the square for the quadratic expression 5x2 40x 15 as shownStep 1 5x2 8x 3Step 2 5x2 8x 16 16 3Step 3 5x 42 16 3Step 4 5x 42 13Step 5 5x 42 65 class=


Answer :

ANSWER

In step 3, he incorrectly wrote the square as (x + 4)². He should have written (x - 4)²

EXPLANATION

When he completed the square, he factored out 5 correctly. Then he found that the second term of the binomial was 4, so he added and subtracted the square of 4, which is 16. But in the next step, he made a mistake with the sign,

Instead of writing (x - 4)², he wrote (x + 4)².

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