Toán Lớp 8: Rút gọn biểu thức : x(x+1)+(x-2)(x+2)-(3x-7)
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Toán Lớp 8: Rút gọn biểu thức : x(x+1)+(x-2)(x+2)-(3x-7)
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Answer
x . (x + 1) + (x – 2) . (x + 2) – (3x – 7)
= x . x + x . 1 + x . (x + 2) – 2 . (x + 2) – 3x + 7
= x^2 + x + x^2 + 2x – 2x – 4 – 3x + 7
= (x^2 + x^2) + (x + 2x – 2x – 3x) + (7 – 4)
= 2x^2 + (3x – 2x – 3x) + 3
= 2x^2 + (x – 3x) + 3
= 2x^2 – 2x + 3
Giải đáp:
x.(x+1)+(x-2).(x+2)-(3x-7)
= x^2 + x + x^2 – 4 – 3x + 7
= (x^2 + x^2) + (x – 3x) + [(-4) + 7]
= 2x^2 – 2x + 3
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