Q8 Q17.) Find the numbers.
2 answers:
Let x = the first number y = the second number ------------------------------------- First: set up the equations. Four times a first number: 4x Decreased by a second number: - y Is 4: = 4 4x - y = 4. The first number increased by: x + three times the second number: 3y is -25: = -25 x + 3y = -25. ------------------------ You can make your system of equations now. 4x - y = 4 x + 3y = -25 I would use substitution to solve these. To do substitution, isolate a variable first, in one of the equations. I would probably isolate x in the second equation. x + 3y = -25 x = -25 - 3y Now, you can substitute -25 - 3y into 4x - y = 4, as x. 4x - y = 4 4(-25 - 3y) - y = 4 Now just solve for y. -100 - 12y - y = 4 -13y = 104 y = -8 Now, you can put -8 as y into one of the original equations, I'll just use 4x - y = 4. 4x - y = 4 4x - (-8) = 4 4x + 8 = 4 4x = -4 x = -1 So the first number is -1, and the second -2.
let x be 1st no. and y be the 2nd no.
so 4x - y = 4
and x + 3y = -25
re-arrange first eqn y = 4x - 4
substitute y into second eqn
x + 3(4x - 4) = -25
13x - 12 = -25
13x = -13
x = -1
y = 4(-1 - 1) = -8
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