1.Tính(tính nhanh nếu có thể)
a. A= (1/3 – 8/15 – 1/7) + (2/3 + -7/15 + 8/7)
b. B= 0.25 + 3/5 -(1/8 – 2/5 + 5/4)
2. Tìm x, biết:
a.x mũ x-1=16
b.(x-2)mũ2 = 25
Mong các bạn giúp mik
1.Tính(tính nhanh nếu có thể)
a. A= (1/3 – 8/15 – 1/7) + (2/3 + -7/15 + 8/7)
b. B= 0.25 + 3/5 -(1/8 – 2/5 + 5/4)
2. Tìm x, biết:
a.x mũ x-1=16
b.(x-2)mũ2 = 25
Mong các bạn giúp mik
`1.`
`a) A= (1/3 – 8/15 – 1/7) + [2/3 + (-7/15) + 8/7]`
`A= 1/3 – 8/15 – 1/7 + 2/3 -7/15 + 8/7`
`A=(1/3+2/3)-(8/15+7/15)+(8/7-1/7)`
`A= 3/3 – 15/15 + 7/7`
`A= 1 – 1 + 1`
`A= 1.`
`b) B= 0,25 + 3/5 -(1/8 – 2/5 + 5/4)`
`B=1/4 + 3/5 – 1/8 + 2/5 -5/4`
`B=(1/4-5/4)+(2/5+3/5) – 1/8`
`B= -4/4 + 5/5 -1/8`
`B=-1+1-1/8`
`B=0-1/8`
`B=-1/8.`
Nếu đề là:
`b) B= 0.25 + 3/5 -(1/8 – 2/5 + 5/4)`
`B=0 + 3/5 – 1/8 + 2/5 -5/4`
`B=-(1/8+5/4)+(2/5+3/5)`
`B=-(1/8+10/8)+5/5`
`B=-11/8+1`
`B=-11/8+8/8`
`B=-3/8.`
`2.`
`a) x^x-1=16`
`b)(x-2)^2 = 25`
`⇔(x-2)^2=(-5)^2=5^2`
`⇒` \(\left[ \begin{array}{l}x-2=5\\x-2=-5\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=5+2\\x=-5+2\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=7\\x=-3\end{array} \right.\)
Vậy `x∈{-3;7}.`
Bạn viết lại đề bài 2a nha
Bài $1$.
$a$) `A = (1/3 – 8/{15} – 1/7) + (2/3 + {-7}/{15} + 8/7)`
`⇔ A = 1/3 – 8/{15} – 1/7 + 2/3 – 7/{15} + 8/7`
`⇔ A = 1 – 1 + 1`
`⇔ A = 1`
$b$) `B = 0,25 + 3/5 – (1/8 – 2/5 + 5/4)`
`⇔ B = 1/4 + 3/5 – 1/8 + 2/5 – 5/4`
`⇔ B = -1 + 1 – 1/8`
`⇔ B = -1/8`
Bài $2$.
$b$) $(x-2)^2 = 25$
$⇔ x-2 = ± 5$
$⇒ x$ $∈$ `{-3;7}`
Vậy $x$ $∈$ `{-3;7}`