Q. A line with equation (3k+2)y+5x=7 has the same gradient as the line y+(3−2k)x=8. Find the value of k where k>0.
Rearrange equation for gradient: To find the gradient of the first line, we need to rearrange the equation (3k+2)y+5x=7 into the slope-intercept formy=mx+b, where m is the gradient.
Isolate y-term: First, we isolate the y-term on one side of the equation:(3k+2)y=−5x+7
Find gradient of first line: Next, we divide both sides by (3k+2) to solve for y:y=3k+2−5x+7
Rearrange second line equation: The gradient of the first line is the coefficient of x, which is −3k+25.
Isolate y-term: Now, we find the gradient of the second line by rearranging y+(3−2k)x=8 into the slope-intercept form.
Find gradient of second line: We isolate the y-term on one side of the equation:y=−(3−2k)x+8
Set gradients equal: The gradient of the second line is the coefficient of x, which is −(3−2k).
Clear fraction: Since the two lines have the same gradient, we set the gradients equal to each other:−3k+25=−13−2k
Expand equation: We can remove the negative signs from both sides of the equation: 3k+25=3−2k
Combine like terms: Next, we multiply both sides by (3k+2) to clear the fraction:5=(3−2k)(3k+2)
Move terms to one side: We expand the right side of the equation: 5=9k+6−6k2−4k
Solve quadratic equation: Combine like terms on the right side: 5=−6k2+5k+6
Calculate discriminant: We move all terms to one side to set the equation to zero:0=−6k2+5k+6−5
Calculate possible values for k: Simplify the equation:0=−6k2+5k+1
Calculate possible values for k: Now, we solve the quadratic equation for k. Since we are looking for k > 0, we can use the quadratic formula:k = 2a−b±b2−4acwhere a = −6, b = 5, and c = 1.
Identify valid solution: Calculate the discriminant (b2−4ac):Discriminant = (5)2−4(−6)(1)=25+24=49
Identify valid solution: Calculate the discriminant (b2−4ac):Discriminant=(5)2−4(−6)(1)=25+24=49Calculate the two possible values for k:k=2⋅−6−5±49
Identify valid solution: Calculate the discriminant (b2−4ac):Discriminant=(5)2−4(−6)(1)=25+24=49Calculate the two possible values for k:k=2⋅−6−5±49Simplify the square root of the discriminant:k=−12−5±7
Identify valid solution: Calculate the discriminant (b2−4ac):Discriminant=(5)2−4(−6)(1)=25+24=49Calculate the two possible values for k:k=2×−6−5±49Simplify the square root of the discriminant:k=−12−5±7Calculate the two possible values for k:k1=−12−5+7=−122=−61k2=−12−5−7=−12−12=1
Identify valid solution: Calculate the discriminant (b2−4ac):Discriminant=(5)2−4(−6)(1)=25+24=49Calculate the two possible values for k:k=2⋅−6−5±49Simplify the square root of the discriminant:k=−12−5±7Calculate the two possible values for k:k1=−12−5+7=−122=−61k2=−12−5−7=−12−12=1Since we are looking for k > 0, the only valid solution is k=1.
More problems from Write the equation of a linear function