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受欢迎的代数 >

化简 (4x^2+8x+15)+(x^2-x-27)-(x+5)(x-7)

解答

化简

(4 x^{2} + 8 x + 15) + (x^{2} - x - 27) - (x + 5) (x - 7)

解答

4 x^{2} + 9 x + 23

求解步骤

(4 x^{2} + 8 x + 15) + (x^{2} - x - 27) - (x + 5) (x - 7)

化简

(4 x^{2} + 8 x + 15) + (x^{2} - x - 27) - (x + 5) (x - 7) : 4 x^{2} + 8 x + 15 + x^{2} - x - 27 - (x + 5) (x - 7)

= 4 x^{2} + 8 x + 15 + x^{2} - x - 27 - (x + 5) (x - 7)

对同类项分组

= 4 x^{2} + x^{2} + 8 x - x - (x + 5) (x - 7) + 15 - 27

同类项相加:

4 x^{2} + x^{2} = 5 x^{2}

= 5 x^{2} + 8 x - x - (x + 5) (x - 7) + 15 - 27

同类项相加:

8 x - x = 7 x

= 5 x^{2} + 7 x - (x + 5) (x - 7) + 15 - 27

数字相减:

15 - 27 = - 12

= 5 x^{2} + 7 x - (x + 5) (x - 7) - 12

展开

- (x + 5) (x - 7) : - x^{2} + 2 x + 35

= 5 x^{2} + 7 x - x^{2} + 2 x + 35 - 12

对同类项分组

= 5 x^{2} - x^{2} + 7 x + 2 x + 35 - 12

同类项相加:

5 x^{2} - x^{2} = 4 x^{2}

= 4 x^{2} + 7 x + 2 x + 35 - 12

同类项相加:

7 x + 2 x = 9 x

= 4 x^{2} + 9 x + 35 - 12

数字相减:

35 - 12 = 23

= 4 x^{2} + 9 x + 23

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