Câu hỏi của Sách Giáo Khoa

Question

Tìm $y$, biết :

a) $y+30\%y=-1,3$

b) $y-25\%y=\dfrac{1}{2}$

c) $3\dfrac{1}{3}y+16\dfrac{3}{4}=-13,25$

Nguyễn Lưu Vũ Quang · Accepted Answer

a) $y+30\%y=-1.3$

$y+\dfrac{3}{10}y=\dfrac{-13}{10}$

$y\left(1+\dfrac{3}{10}\right)=\dfrac{-13}{10}$

$y\left(\dfrac{10}{10}+\dfrac{3}{10}\right)=\dfrac{-13}{10}$

$y\cdot\dfrac{13}{10}=\dfrac{-13}{10}$

$y=\dfrac{-13}{10}:\dfrac{13}{10}$

$y=\dfrac{-13}{10}\cdot\dfrac{10}{13}$

$y=-1$

Vậy $y=-1$.

b) $y-25\%y=\dfrac{1}{2}$

$y-\dfrac{1}{4}y=\dfrac{1}{2}$

$y\left(1-\dfrac{1}{4}\right)=\dfrac{1}{2}$

$y\left(\dfrac{4}{4}-\dfrac{1}{4}\right)=\dfrac{1}{2}$

$y\cdot\dfrac{3}{4}=\dfrac{1}{2}$

$y=\dfrac{1}{2}:\dfrac{3}{4}$

$y=\dfrac{1}{2}\cdot\dfrac{4}{3}$

$y=\dfrac{2}{3}$

Vậy $y=\dfrac{2}{3}$.

c) $3\dfrac{1}{3}y+16\dfrac{3}{4}=-13.25$

$\dfrac{10}{3}y+\dfrac{67}{4}=\dfrac{-53}{4}$

$\dfrac{10}{3}y=\dfrac{-53}{4}-\dfrac{67}{4}$

$\dfrac{10}{3}y=-30$

$y=-30:\dfrac{10}{3}$

$y=-30\cdot\dfrac{3}{10}$

$y=-9$

Vậy $y=-9$.Câu trả lời: a) $y+30\%y=-1.3$

$y+\dfrac{3}{10}y=\dfrac{-13}{10}$

$y\left(1+\dfrac{3}{10}\right)=\dfrac{-13}{10}$

$y\left(\dfrac{10}{10}+\dfrac{3}{10}\right)=\dfrac{-13}{10}$

$y\cdot\dfrac{13}{10}=\dfrac{-13}{10}$

$y=\dfrac{-13}{10}:\dfrac{13}{10}$

$y=\dfrac{-13}{10}\cdot\dfrac{10}{13}$

$y=-1$

Vậy $y=-1$.

b) $y-25\%y=\dfrac{1}{2}$

$y-\dfrac{1}{4}y=\dfrac{1}{2}$

$y\left(1-\dfrac{1}{4}\right)=\dfrac{1}{2}$

$y\left(\dfrac{4}{4}-\dfrac{1}{4}\right)=\dfrac{1}{2}$

$y\cdot\dfrac{3}{4}=\dfrac{1}{2}$

$y=\dfrac{1}{2}:\dfrac{3}{4}$

$y=\dfrac{1}{2}\cdot\dfrac{4}{3}$

$y=\dfrac{2}{3}$

Vậy $y=\dfrac{2}{3}$.

c) $3\dfrac{1}{3}y+16\dfrac{3}{4}=-13.25$

$\dfrac{10}{3}y+\dfrac{67}{4}=\dfrac{-53}{4}$

$\dfrac{10}{3}y=\dfrac{-53}{4}-\dfrac{67}{4}$

$\dfrac{10}{3}y=-30$

$y=-30:\dfrac{10}{3}$

$y=-30\cdot\dfrac{3}{10}$

$y=-9$

Vậy $y=-9$.

MINH QUÂN ĐÀO · Answer

a) y+30%y=−1.3y+30%y=−1.3

y+310y=−1310y+310y=−1310

y(1+310)=−1310y(1+310)=−1310

y(1010+310)=−1310y(1010+310)=−1310

y⋅1310=−1310y⋅1310=−1310

y=−1310:1310y=−1310:1310

y=−1310⋅1013y=−1310⋅1013

y=−1y=−1

Vậy y=−1y=−1.

b) y−25%y=12y−25%y=12

y−14y=12y−14y=12

y(1−14)=12y(1−14)=12

y(44−14)=12y(44−14)=12

y⋅34=12y⋅34=12

y=12:34y=12:34

y=12⋅43y=12⋅43

y=23y=23

Vậy y=23y=23.

c) 313y+1634=−13.25313y+1634=−13.25

103y+674=−534103y+674=−534

103y=−534−674103y=−534−674

103y=−30103y=−30

y=−30:103y=−30:103

y=−30⋅310y=−30⋅310

y=−9y=−9

Vậy y=−9y=−9.Câu trả lời: a) y+30%y=−1.3y+30%y=−1.3