Answer: Option C) Raj forgot the negative when substituting -15+9x for y.
Solution:
(1) 9x-y=15
(2) 2x+8y=28
Isolating y in the first equation. Subtracting 9x both sides of the equation:
(1) 9x-y-9x=15-9x
Subtracting:
(1) -y=15-9x
Multiplying both sides of the equation by -1:
(1) (-1)(-y)=(-1)(15-9x)
(1) y=-15+9x
Then Raj found the value of y. It's not option D.
Substitutng y by -15+9x in the second equation:
(2) 2x+8(-15+9x)=28
Then option C) is the answer: Raj forgot the negative when substituting -15+9x for y.
Eliminating the parentheses applying the distributive property in the multiplication:
(2) 2x-120+72x=28
Adding similar terms:
(2) 74x-120=28
Solving for x. Adding 120 both sides of the equation:
(2) 74x-120+120=28+120
Adding:
(2) 74x=148
Dividing both sides of the equation by 74:
(2) 74x/74=148/74
Dividing:
(2) x=2
Solving for y: Replacing x by 2 in the first equation:
(1) y=-15+9x
(1) y=-15+9(2)
Multiplying:
(1) y=-15+18
Subtracting:
(1) y=3
The standard form would be y = 7x^2 - 42x + 67
Answer:1296
Step-by-step explanation:1200*.04=96
1200+96=1296
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Answer:
Step-by-step explanation:
x + y = 25 ...........................(1)
{4x + 2y =64} / 2 divide the equation by 2
2x + y = 32 ........................(3)
Step Two
subtract (1) from (3)
2x + y = 32
x + y = 25
x = 7
Therefore from equation 1 we get x + y = 25
but x = 7
7 + y = 25 Subtract 7 from both sides.
y = 25 - 7
y = 18
Check
4*x + 2*y = 64
4*7 + 2*18 =? 64
28 + 36 = ? 64
64 = 64
The checks out to be the right answer.
