13. 已知$x^2 - 2x = 2$,代数式$(x - 1)^2 + 2022 =$
$2025$
.答案
13. 2025 【点拨】本题考查完全平方公式,代数式求值.
【解析】$\because x^2-2x=2$,$\therefore (x-1)^2 +2022 =x^2-2x+1+2022=2+1+2022=2025$. 故答案为2025.
【解析】$\because x^2-2x=2$,$\therefore (x-1)^2 +2022 =x^2-2x+1+2022=2+1+2022=2025$. 故答案为2025.
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答案
未检测到有效的数学题干信息,请补充完整具体的题目内容后,即可为您提供符合苏科版七年级下册学段要求的规范解题过程。
15. 若$(x^2 + mx)(x^2 + 2x - n)$的积中不含$x^2$的项与$x^3$的项,则代数式$mn$的值为________.
答案
15. 8 【点拨】本题考查多项式的乘法中不含某项问题.
【解析】$(x^2+mx)(x^2+2x-n)=x^4+2x^3-nx^2+mx^3+2mx^2-mnx=x^4+(m+2)x^3+(2m-n)x^2-mnx$.
$\because (x^2+mx)(x^2+2x-n)$的积中不含$x^2$和$x^3$的项,$\therefore m+2=0,2m-n=0$,$\therefore m=-2,n=-4$,$\therefore mn=-2×(-4)=8$. 故答案为8.
【解析】$(x^2+mx)(x^2+2x-n)=x^4+2x^3-nx^2+mx^3+2mx^2-mnx=x^4+(m+2)x^3+(2m-n)x^2-mnx$.
$\because (x^2+mx)(x^2+2x-n)$的积中不含$x^2$和$x^3$的项,$\therefore m+2=0,2m-n=0$,$\therefore m=-2,n=-4$,$\therefore mn=-2×(-4)=8$. 故答案为8.
16. 有两个正方形A,B,现将B放在A的内部得图1,将A,B并列放置后构造新的正方形得图2.若图1和图2中阴影部分的面积分别为5和35,则图2的面积为

$75$
.答案
16. 75 【点拨】本题考查完全平方公式的应用.
【解析】设正方形A和B的边长分别为$a$和$b$,$\therefore$ 图1阴影部分面积为$(a-b)^2=5$,即$a^2-2ab+b^2=5$,图2阴影部分面积为$b(a+b)+b(a-b)=35$,即$2ab=35$,$\therefore a^2+b^2=40$,$\therefore$ 图2的面积为$(a+b)^2=a^2+2ab+b^2=40+35=75$. 故答案为75.
【解析】设正方形A和B的边长分别为$a$和$b$,$\therefore$ 图1阴影部分面积为$(a-b)^2=5$,即$a^2-2ab+b^2=5$,图2阴影部分面积为$b(a+b)+b(a-b)=35$,即$2ab=35$,$\therefore a^2+b^2=40$,$\therefore$ 图2的面积为$(a+b)^2=a^2+2ab+b^2=40+35=75$. 故答案为75.
三、解答题(本大题共9小题,共68分.解答应写出过程)
17. (9分)计算:
(1)$b· b^{3}· b^{5}$;
(2)$(x-y)^{3}(y-x)^{2}$;

(3)$(-2)^{2}+(-2)^{0}+(-\dfrac{1}{2})^{-1}$.
17. (9分)计算:
(1)$b· b^{3}· b^{5}$;
(2)$(x-y)^{3}(y-x)^{2}$;
(3)$(-2)^{2}+(-2)^{0}+(-\dfrac{1}{2})^{-1}$.
答案
17. 【点拨】本题考查同底数幂的乘法,有理数的混合运算,熟练掌握运算法则是解题的关键.
【解析】(1)$b · b^3 · b^5 = b^{1+3+5}=b^9$.
(2)$(x-y)^3(y-x)^2=(x-y)^3(x-y)^2=(x-y)^{3+2}=(x-y)^5$.
(3)$(-2)^2 + (-2)^0 + (-\frac{1}{2})^{-1}=4+1-2=3$.
【解析】(1)$b · b^3 · b^5 = b^{1+3+5}=b^9$.
(2)$(x-y)^3(y-x)^2=(x-y)^3(x-y)^2=(x-y)^{3+2}=(x-y)^5$.
(3)$(-2)^2 + (-2)^0 + (-\frac{1}{2})^{-1}=4+1-2=3$.
18. (16 分)计算:
(1)$(y - \dfrac{1}{2})^2$;
(2)$(2x - y)(3x - 2y) + 4xy$;
(3)$(x + y - 2)(x - y + 2)$;
(4)$(2x - 1)(2x + 1)(4x^2 + 1)$.
·8·
(1)$(y - \dfrac{1}{2})^2$;
(2)$(2x - y)(3x - 2y) + 4xy$;
(3)$(x + y - 2)(x - y + 2)$;
(4)$(2x - 1)(2x + 1)(4x^2 + 1)$.
·8·
答案
18. 【点拨】本题考查完全平方公式,平方差公式和多项式乘多项式.
【解析】(1)$(y-\frac{1}{2})^2 = y^2 - y + \frac{1}{4}$.
(2)$(2x-y)(3x-2y)+4xy$
$=6x^2-4xy-3xy+2y^2+4xy$
$=6x^2-3xy+2y^2$.
(3)$(x+y-2)(x-y+2)$
$=[x+(y-2)][x-(y-2)]$
$=x^2-(y-2)^2$
$=x^2-(y^2-4y+4)$
$=x^2-y^2+4y-4$.
(4)$(2x-1)(2x+1)(4x^2+1)$
$=(4x^2-1)(4x^2+1)$
$=16x^4-1$.
【解析】(1)$(y-\frac{1}{2})^2 = y^2 - y + \frac{1}{4}$.
(2)$(2x-y)(3x-2y)+4xy$
$=6x^2-4xy-3xy+2y^2+4xy$
$=6x^2-3xy+2y^2$.
(3)$(x+y-2)(x-y+2)$
$=[x+(y-2)][x-(y-2)]$
$=x^2-(y-2)^2$
$=x^2-(y^2-4y+4)$
$=x^2-y^2+4y-4$.
(4)$(2x-1)(2x+1)(4x^2+1)$
$=(4x^2-1)(4x^2+1)$
$=16x^4-1$.
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