Answer:
1)
(x + 3)(x + 4) = x^2 + 4x + 3x + 12 = x^2 + 7x + 12
Instead of multiplying 3 and 4 the student added them which gave them the answer of 7 when the correct answer is 12.
2)
a) x^2 + x - 2
b) x^2 - 7x + 10
c) 4x^2 - 1
d) x^2 + 10x + 25
Step-by-step explanation:
a. (x - 1)(x + 2)
x(x) - 1(x) + 2(x) - 1(2)
x^2 - 1x + 2x - 2
x^2 + x - 2
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b. (x - 5)(x - 2)
x(x) - 5(x) - 2(x) - 5(-2)
x^2 - 5x - 2x + 10
x^2 - 7x + 10
------------------------------------------
c. (2x + 1)(2x - 1)
2x(2x) + 1(2x) - 1(2x) + 1(-1)
4x^2 + 2x - 2x - 1
4x^2 - 1
------------------------------------------
d. (x + 5)^2
(x + 5)(x + 5)
x(x) + 5(x) + 5(x) + 5(5)
x^2 + 5x + 5x + 25
x^2 + 10x + 25
