a*x+a*y+b*x+b*y

= a*(x+y)+b*(x+y)

= a*(-17)+b*(-17)              (vì x+y=-17)

=(-17)*(a+b)

=(-17)*(-2)                        (vì a+b=-2)

=34

\(a)y\times3+y\times12,5=825\)

\(\Rightarrow y\times\left(3+12,5\right)=825\)

\(\Rightarrow y\times15,5=825\)

\(\Rightarrow y=825:15,5\)

\(\Rightarrow y=5\frac{10}{31}\)

\(b)y\times3+y:0,5=12,85\)

\(\Rightarrow y\times3+y:\frac{1}{2}=12,85\)

\(\Rightarrow y\times3+y\times2=12,85\)

\(\Rightarrow y\times\left(3+2\right)=12,85\)

\(\Rightarrow y\times5=12,85\)

\(\Rightarrow y=12,85:5\)

\(\Rightarrow y=2,57\)

9.75.y-y+y.1.25=2,5.1,5

y. (9,75-1+1,25)=3,75

y.10=3,75

y=3,75:10

y=0,375

4,5dm  =              m 

Mot mieng dat hinh thang vuong co day lon la 48m, day be bang 2/3 day lon va duong cao day be .Nguoi ta mo rong day be de duoc mieng dat hinh chu nhat nhu hinh  ve.

a . tinh dien h manh dat luc dau .     b.tinh dien h mang dat khi  rong .

\(\frac{1}{3}\cdot y+2=\frac{1}{5}\cdot y+\frac{7}{2}\)

\(=>\frac{1}{3}\cdot y-\frac{1}{5}\cdot y=\frac{7}{2}-2\)

\(=>y\cdot\left(\frac{1}{3}-\frac{1}{5}\right)=\frac{3}{2}\)

\(=>y\cdot\frac{2}{15}=\frac{3}{2}\)

\(=>y=\frac{3}{2}:\frac{2}{15}=\frac{45}{4}\)

Hai phần chín cộng ích bằng một

theo de bai ta co 1/3.y+2=1/5.y+7/2

=>y/3+2=y/5+7/2

=>y+6/3=2y+35/10

=>6y+105=10y+60

=>16y=165

=>y=165/16

y x 326,63 + 245,37 x y = 429

y x ( 326,63 + 245,37 ) = 429

y x 572 = 429

y = 429 : 572

y = 0,75

\(y\cdot326,63+245.37\cdot y=429\)

\(y\cdot\left(326,63+245,37\right)=429\)

\(y\cdot572=429\)

\(y=429:572=\frac{3}{4}\)

y * 326.63 + 245.37 * y = 429

y * ( 326.63 + 245.37 ) = 429

y * 572 = 429

y = \(\frac{429}{572}\)

\(y=\frac{3}{4}\)