Question

tìm x bt

a,78-3.(x-1)=15

b,(7x-11)³=2⁵.5²+200

c,5.(3x-13)=5⁴

^{d,3.(5x-13)=3^4}

Answer 1

mẫu ý a)

78-3(x-1)=15

<=>78-3x+3=15

<=>3x=81-15=66

<=>x=22

Answer 2

a)\(78-3\left(x-1\right)=15\)

\(3\left(x-1\right)=78-15\)

\(3\left(x-1\right)=63\)

\(x-1=63:3\)

\(x-1=21\)

\(x=21+1=22\)

b. \(\left(7x-11\right)^3=2^5.5^2+200\)

\(\left(7x-11\right)^3=32.25+200\)

\(\left(7x-11\right)^3=800+200=1000\)

\(\left(7x-11\right)^3=10^3\)

\(\Rightarrow7x-11=10\)

\(7x=10+11\)

\(7x=21\)

\(x=21:7=3\)

c.\(5.\left(3x-13\right)=5^4\)

\(3x-13=5^4:5\)

\(3x-13=5^3=125\)

\(3x=125+13=138\)

\(x=138:3=46\)

d.\(3.\left(5x-13\right)=3^4\)

\(5x-13=3^4:3=3^3\)

\(5x-13=27\)

\(5x=27+13=40\)

\(x=40:5=8\)