Tìm x : a) (7x-35).(-4x-20)=0 b) -12+2(-x+7)=-18 c) 95-5.(-24-x)=-5 TOÁN 6 ạ. 18/07/2021 Bởi Aubrey Tìm x : a) (7x-35).(-4x-20)=0 b) -12+2(-x+7)=-18 c) 95-5.(-24-x)=-5 TOÁN 6 ạ.
a) (7x-35).(-4x-20)=0 =>\(\left[ \begin{array}{1}7x-35=0\\(-4)x-20=0\end{array} \right.\) =>\(\left[ \begin{array}{l}x=5\\x=-5\end{array} \right.\) b) -12+2(-x+7)=-18 =>2×(-x+7)=(-12)+(-18) =>2×(-x+7)=-30 =>-x+7=-30÷2 =>-x+7=-15 =>-x=-15-7 =>-x=-22 =>x=22 c,95-5.(-24-x)=-5 =>5×(-24-x)=95-(-5) =>5×(-24-x)=-100 =>(-24-x)=5×(-100) =>(-24-x)=-500 =>-x=(-24)-(-500) =>-x=-524 =>x=524 Bình luận
a) (7x-35).(-4x-20)=0
=>\(\left[ \begin{array}{1}7x-35=0\\(-4)x-20=0\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=5\\x=-5\end{array} \right.\)
b) -12+2(-x+7)=-18
=>2×(-x+7)=(-12)+(-18)
=>2×(-x+7)=-30
=>-x+7=-30÷2
=>-x+7=-15
=>-x=-15-7
=>-x=-22
=>x=22
c,95-5.(-24-x)=-5
=>5×(-24-x)=95-(-5)
=>5×(-24-x)=-100
=>(-24-x)=5×(-100)
=>(-24-x)=-500
=>-x=(-24)-(-500)
=>-x=-524
=>x=524
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