Toán Lớp 8: Rút gọn các biểu thức :
a)5(x-2)+2(x+3)
b)(x+1)^2-(x-5)(x+2)
c)(x+7)(x-7)-(x-1)(x+1)
d)(x+5)^2+x(2x+5)^2.(2x+5)(2x-1)
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Toán Lớp 8: Rút gọn các biểu thức :
a)5(x-2)+2(x+3)
b)(x+1)^2-(x-5)(x+2)
c)(x+7)(x-7)-(x-1)(x+1)
d)(x+5)^2+x(2x+5)^2.(2x+5)(2x-1)
Comments ( 1 )
Giải đáp+Lời giải và giải thích chi tiết:
$a) 5(x-2)+2(x+3)=5x-10+2x+6=7x-4$
$b) (x+1)^2-(x-5)(x+2)=x^2+2x+1-(x^2+2x-5x-10)=x^2+2x+1-x^2-2x+5x+10=5x+11$
$c) (x+7)(x-7)-(x-1)(x+1)=x^2-49-(x^2-1)=x^2-49-x^2+1=-48$
$d) (x+5)^2+x(2x+5)^2.(2x+5)(2x-1)=x^2+10x+25+x(4x^2 +20x+25).(4x^2-2x+10x-5)=x^2+10x+25+x(4x^2 +20x+25)(4x^2+8x-5)=x^2+10x+25+x(16x^4+32x^3-20x^2+80x^3+160x^2-100x+100x^2+200x-125)=x^2 +10x+25+x(16x^4+112x^3+240x^2+100x-125)=x^2+10x+25+16x^5+112x^4+240x^3+100x^2-125x=16x^5+112x^4 +240x^3+101x^2-125x$
$\text{Câu d mình ko chắc nha}$