Đáp án+Giải thích các bước giải:
41
`a) (x-4)²-36=0`
`⇔(x-4)²-6^2=0`
`⇔(x-4-6)(x-4+6)=0`
`⇔(x-10)(x+2)=0`
`⇔ `\(\left[ \begin{array}{l}x-10=0\\x+2=0\end{array} \right.\) `⇔ `\(\left[ \begin{array}{l}x=10\\x=-2\end{array} \right.\)
`b) (x+8)²=121`
`⇔(x+8)²-121=0`
`⇔(x+8)²-11²=0`
`⇔(x+8-11)(x+8+11)=0`
`⇔(x-3)(x+19)=0`
`<=>`\(\left[ \begin{array}{l}x-3=0\\x+19=0\end{array} \right.\)`<=>` \(\left[ \begin{array}{l}x=3\\x=-19\end{array} \right.\)
`c) x²+8x+16=0`
`⇔(x+4)²=0`
`⇔x+4=0`
`⇔x=-4`
`d)4x²-12x+9=0`
`⇔(2x-3)²=0`
`⇔2x-3=0`
`⇔2x=3`
`⇔x=`$\dfrac{3}{2}$
`42`
`a) 75²-25²=(75-25)(75+25)=50×100=5000`
`b) 53²-47²=(53-47)(53+47)=6×100=600`
`c) 31,8²-2×31,8×21,8+21,8²=(31,8-21,8)²=10²=100`
`d) 58,2²+2×58,2×41,8+41,8²=(58,2+41,8)²=100²=10000`
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