Tìm số nguyên x, y biết rằng :
a ) 11 – ( – 52 + 2 . x ) = 97
b ) ( x + 7 ) : 3 – 14 = – 29
c ) ( – 33 + 42 ) . x² = 89 – ( – 136 )
d ) xy – 2x + y = 13
Tìm số nguyên x, y biết rằng : a ) 11 – ( – 52 + 2 . x ) = 97 b ) ( x + 7 ) : 3 – 14 = – 29 c ) ( – 33 + 42 ) . x² = 89 – ( – 136 ) d ) xy – 2x + y
By Josephine
a, 11-( -52+2x)= 97
⇔ 11+52-2x= 97
⇔ -2x= 34
⇔ x= -17
b, ( x+7):3-14= -29
⇔ ( x+7):3= -15
⇔ x+7= -45
⇔ x= -52
c, ( -33+42).x²= 89-( -136)
⇔ 9x²= 225
⇔ x²= 25
⇔ x= ±5
d, xy-2x+y= 13
⇔ x.( y-2)+y-2= 11
⇔ ( x+1).( y-2)= 11= 1.11= 11.1= ( -1).( -11)= ( -11).( -1)
Bạn tự kẻ bảng nha
a ) 11 – ( – 52 + 2 . x ) = 97
⇒-52+2x=-86
⇒2x=-34
⇒x=-17
b ) ( x + 7 ) : 3 – 14 = – 29
⇒(x+7):3=-15
⇒x+7=-5
⇒x=-12
c ) ( – 33 + 42 ) . x² = 89 – ( – 136 )
⇒(-33+42).x²=225
⇒9.x²=225
⇒x²=25
⇒x=±5
d ) xy – 2x + y = 13
⇒x(y-2)=13-y
Nếu y-2=0⇒y=2⇒0x=11 (loại)
Chia 2 vế cho y-2$\neq$0
Ta có: x=$\frac{13-y}{y-2}$
⇒x=$-1+\frac{11}{y-2}$
⇒y-2∈Ư(11)={±1;±11}
y-2=1⇒y=3⇒x=10 ™
y-2=-1⇒y=1⇒x=-12 ™
y-2=11⇒y=13⇒x=0 ™
y-2=-11⇒y=-9⇒x=-2 ™
Vậy (x,y)∈{(10;3);(-12;3);(0;13);(-2;-9)}