Toán Lớp 8: d) 2(x+5)-x2-5x=0 e)x2+5x-6=0 g)x2-10x=-25

Question

Toán Lớp 8:  d) 2(x+5)-x2-5x=0 e)x2+5x-6=0 g)x2-10x=-25

phuongthaongoc · Answer

Giải đáp:       Lời giải và giải thích chi tiết:    $d, 2(x+5)-x^{2}-5x=0$   $=>2(x+5)-x(x+5)=0$   $=>(x+5)(2-x)=0$   => ( left[  begin{array}{l}x+5=0  2-x=0 end{array}  right. )   => ( left[  begin{array}{l}x=-5  x=2 end{array}  right. )   $e, x^{2}+5x-6=0$   $=>x^{2}-x+6x-6=0$   $=>x(x-1)+6(x-1)=0$   $=>(x-1)(x+6)=0$   => ( left[  begin{array}{l}x-1=0  x+6=0 end{array}  right. )   => ( left[  begin{array}{l}x=1  x=-6 end{array}  right. )   $g,x^{2}-10x=-25$   $=>x^{2}-10x+25=0$   $=>(x-5)^{2}=0$   $=>x-5=0$   $=>x=5$

tuyen98 · Answer

d) 2(x+5) -x^2 -5x=0           2(x+5)-x(x+5)=0            (2-x)(x+5)=0   &rArr; ( left[  begin{array}{l}2-x=0  x+5=0 end{array}  right. )    &rArr; ( left[  begin{array}{l}x=2  x=-5 end{array}  right. )           text{Vậy x=2 hoặc x=-5}   e) x^2+5x-6=0        x^2+x-6x-6=0        x(x+1)-6(x+1)=0      (x-6)(x+1)=0   &rArr; ( left[  begin{array}{l}x-6=0  x+1=0 end{array}  right. )    &rArr; ( left[  begin{array}{l}x=6  x=-1 end{array}  right. )           text{Vậy x=6 hoặc x=-1}   g) x^2 - 10x = -25       x^2- 10x + 25-0       (x-5)^2 =0           &rArr;x-5=0            &rArr; x=5            Vậy x=5