A student was asked to find the square of 7x+3. The student quickly wrote (7x+3) ^2=49x^2+9. Identify the students error and provide the correct answer.

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Humberto Lucas

18 April, 10:07

A student was asked to find the square of 7x+3. The student quickly wrote (7x+3) ^2=49x^2+9. Identify the students error and provide the correct answer.

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Alyson · Answer 1

The student did not use the FOIL method to solve the binomials. The FOIL method is used to multiply binomials, or to multiply (x + 3) by (3x - 12).

Correct Answer: (7x+3) ^2 = 49x^2 + 42x + 9

Explanation: Use the FOIL method: First, Outer, Inner, Last

(7x+3) (7x+3)

First: (7x) (7x) = 49x^2

Outer: (7x) (3) = 21x

Inner: (3) (7x) = 21x

Last: (3) (3) = 9

49x^2 + 21x + 21x + 9 = 49x^2 + 42x + 9